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General mill or warehouse fumigation ________ ) IBrocedureses saeco, 2 ae 36 Requirements for a successful fumigation _ 5 | Fumigation of various commodities___________ 38 Preparing the building for fumigation ____ 5 Confectionery esterase et O08 eae 39 Desirability of a high temperature during Vault fumigation for nuts__.-_________ 40 (Ho) Mob TaN EHO) ee eee eee aoe 9 Vacuum fumigation for nut meats____ 40 Byfechor wind velocitive.22 4-2) ee 9 Fumigation of sacked peanuts in Effect of light or darkness_______---__-_--_ se) {rel Sh ticarsi ees ee eS eee 41 Chorceotatumicant == oss] == eee ) Fumigation schedule for candy Quantity of fumigant needed__-__________ 10 LaACtORICSH he ete ett, eee ae 4] Applyine the tum gant. 25. aan ue 10 DOSAGES Ree Calas NO tinidan me” Salien: 41 Ventilating the building after a fumiga- BEQUEDTATG UIT pe ees eens EE Tae Sah ee ae 41 (EIKO) 0s. itm eee oii emamenrne 4 oh at ae De ent ee ean 10 Niobe yal Pe maN No eee 42 Fumigation with hydrocyanic acid gas___ 11 Construction of storage rooms_______- 42 The barrel or pot method____-________ 11 1D) OSA ROS teen Silos 2 nen te ea 44 mhoviquid- method sas. sea a ae 17 Effect of fumigation on furs____-----______ 44 WerdiscoldunethoGsaes= a= eee eae 21 IRWesanGitapesunies seen. ee emer n es 45 The powder method_________________- 23 TLCS UE Geese eee eee 2a 46 Fumigation with chloropicrin____________ 24 Treating the finished products —=s— 46 Fumigation with ethylene oxide-carbon Infestations in warehouses__-----_--__ 47 GOxIGenmiRb une Se ee ee 25 Cured meats and cheeses________-------__ 47 Fumigation with methyl bromide-carbon StOredetob acco merase ee ce ie c ee re ee 47 dioxidounixiunesi =. eene ees ees cee 27 DO Uresee es Vasey Sire oi ce ser ee 49 Fumigation with methyl formate-carbon General mill fumigation______________ 50 dioxid esmixtures=s=—9 se." Hae ees 28 IMOCAUTUIMI atl Onsen =n eee 54 Va tlisaini Sati oneesenns pote nec tee bate 28 Fumigation of flour warenouses_-_____- 55 Use of fumigants suitable also for large Vault fumigation for flour or cereal SDACCS 8s ane er ho: gS le PA 29 TOOUU NS sete Sate Me Vee ee an eg is Ba eee 55 Use of other fumigants_-_---__-__--- uae bel 31 Vacuum fumigation of flour products_ 56 @anbonkdisul phide wean a iaeee eae 31 AR COaimtod = mene “oe Anieys eT Nae ese ers Se 56 Warhbonstetrachloridesss2=- sea 31 @ottonseedsmealiss sae eee 56 Ethylene dichloride_____-__-_-_--_____ 32 | Safeguards to be employed in fumigation work_ 57 Eithylenomox densa oes s- sobs see Gee 32 | First aid for poisoning from hydrocyanic acid IBinginmigahioneek ses a es Th oe eee ee 33 (CRS pom Le eee Ve ee a Reem erat CaS Os Col ee aoe Py SS 58 Vacnuniitmigarion:: 2202-2 2+ oe 33 Shaefer prone-pressure method of artificial Rea Mipmentes 2.4 ln cs ooo 34 TESpIravlonm see wee ee ee sae oe eee 59 INTRODUCTION Insect infestation is frequently a problem of considerable impor- tance in the storage of many types of merchandise. During warm weather or in heated buildings, foodstuffs, cereals, seeds, tobacco, furs, fabrics, etc., are highly susceptible to infestation by insects, and heavy losses are likely to occur unless adequate protection is given them. If cold-storage facilities are available, such commodities can be protected from insect damage by holding them at temperatures below 45° to 50° F. Many times, however, it is impossible or impractical to use cold storage, and it is necessary to resort to fumi* gation. This circular describes various methods by which products in storage or the establishments in which they are manufactured can be protected from insect attack by the use of fumigants. 4964 °—37——_1 2 i CIRCULAR 369, U. 5. DEPT. OF AGRICULTURE In the protection of stored commodities four methods of fumiga- tion are in common use: (1) The general or large-scale fumigation of warehouses and mills (fig. 1), (2) vault fumigation (fie. 2), (8) bin fumigation (fig 3), and (4) vacuum fumigation (fig. 4). Each method is adapted to a certain type of work and will be dis- cussed separately. In most industries a combination of two or more FIGURE 1.—Interior view in flour mill ready for fumigation with hydrocyanic acid gas generated by the barrel method. The eight barrels containing the acid-water mixture Stand in galvanized-iron washtubs, and a “sack of sodium cyanide is ready to be lowered into each barrel. of these methods can be used to advantage; and sometimes special methods, such as fumigation under tarpaulins (fig. 5) or the treat- ment of the individual “pack of a commodity (fig. 6), are developed. GENERAL MILL OR WAREHOUSE FUMIGATION All mills, factories, warehouses, and storage rooms in which ma- terial subject to insect attack is handled become infested at one time or another and need a general fumigation. The managers of many such places realize the importance of maintaining a clean plant and fumigate one or more times a year as a general practice. Others, fearing the trouble and expense, wait until conditions become so bad that they are forced to shut down their mills for a thorough cleaning and fumigation. There is no reason why fumigation should be an expensive opera- tion, for with simple equipment a few intelligent workers can be quickly trained to fumigate most places with no more expense than their time and the bare cost of the materials. INDUSTRIAL FUMIGATION AGAINST INSECTS 23 FIGURE 2.—A battery of three modern steel fumigation vaults, each about 6 by 8 by 10 feet, equipped with apparatus for introducing and withdrawing the fumigant, and for heating and circulating the air within. Such vaults are used for treatment of various commodities, in this instance furs, and not ordinarily for continuous storage. FicurE 3.—A battery of 10 storage bins so constructed that dried-fruit products stored in them can be fumigated, 4 “CIRCULAR 369, U. S. DEPT. OF AGRICULTURE ViGurRE 4.—A vacuum fumigating unit in a large general-merchandise storage warehouse. Since it is located along the railroad siding, susceptible commodities are fumigated as they are unloaded from the freight car and before they are placed in storage rooms, where only fumigated supplies are stored. ai be Ficure 5.—Commodities of various types assembled for export on a modern dock. Carload lots of supplies found slightly infested upon arrival by rail are sometimes fumigated Ce beneath rubberized tarpaulins. While such treatments are not always entirely satisfac- tory, they are resorted to in numerous instances, INDUSTRIAL FUMIGATION AGAINST INSECTS : 5 REQUIREMENTS FOR A SUCCESSFUL FUMIGATION . Success in the fumigation of any large building or enclosure de- pends upon the proper planning and execution of the work, the care- ful preparation of the building, and the correct choice of the fumi- gant and time of its application. The building must be made as nearly gastight as possible in order to avoid waste of gas and to retain a lethal concentration of the fumigant as long as possible. All machinery or special pieces of apparatus must be cleaned and opened up to allow maximum penetration of the gas. The temperature must be high enough to render the insects sus- ceptible to the fumigant and to allow for its most efficient action. FIGURE 6.—While industry in general has not found it feasible to promote insect sanitation by introducing a fumigant into the shipping unit as it moves through the packing machinery, this is a method that has been satisfactorily employed. The fumigant, in liquid form, is automatically introduced in each container just previous to the entry of the commodity and the sealing of the container. The fumigant must be suitable for the building in which it is used and for the contents of the building. The quantity must be great enough to allow for the loss through poor construction of the building, absorption by the contents of the building, and adverse weather conditions. The fumigant must also be properly applied and distributed. The exposure must be long enough to permit maxi- mum penetration and killing effect. Precautions must be taken to see that all persons are out of the building before the fumigation is started, and are kept out during the fumigation and thereafter until the building has been properly ventilated and declared safe to enter. Arrangements should be made for quickly ventilating the building at the end of the fumigation. PREPARING THE BUILDING FOR FUMIGATION It is essential that the building be made as nearly gastight as pos- sible. A modern concrete building having windows with steel frames is excellent for fumigation purposes, since little effort is needed to 6 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE make it reasonably gastight. Doors leading to the outside should be sealed (fig. 7). Ventilators on the roof (fig. 8) or outside walls should also be sealed over, and any windows that are not tight should be sealed around the edges. Old or poorly constructed buildings present a different problem. Both walls and roof must be carefully inspected for cracks or breaks. In certain types of roofs the union be- tween the roof and the walls may be faulty and need to be tightened (figs. 8 and 9). Any loose flashing around chimneys and venti- lators must be re- paired, and ventila- tors and skylights must be sealed over (fig. 8). In some cases it 1s impossible to tighten a window bay the. sondinany, method of wedging and sealing or strip- ping, and the entire aperture must be sealed over (fig. 9). For this purpose a fiber-reinforced wa- terproof building paper is_ excellent. It can be obtained in rolls 300 feet long and from 38 to 7 feet wide. It is a simple matter to tack it over the opening, and the edges can be sealed down with adhesive tape. If this type of paper is not avail- ligurn 7.—Doors to warehouse, and transom, sealed with able, aut good tough old advertising posters cut into strips. Latticed ware- paper can be used house doors in warm climates can be effectively sealed : with three or four thicknesses of such material. and can be applied by a paperhanger or any careful workman. Even newspapers or old advertising posters will sometimes suffice if several layers are used, but the best paper for fumigation purposes is that impregnated with fiber and tar. Loosely fitting window sashes should be sealed with paste and paper, or puttied up with a mixture of flour and oil. For stripping windows that are only slightly loose several types of materials can be used. Rolls of gummed paper, strips of newspaper smeared with 7 INDUSTRIAL FUMIGATION AGAINST INSECTS 7 erease or pasted with flour paste, and rolls of unsterilized adhesive or masking tape, known as “fumigators’ tape”, all have their place. Small doors leading to the exterior of the building can be tight- ened by stripping around the edges with any of the “materials used FIGURE 8.—Skylights and flashings on roof sealed in preparation for fumigation. Al]! ventilators must also be sealed. (Photograph furnished by W. D. Reed.) for the windows. Large sliding or hinged doors that fit imperfectly, or elevator-shaft openings, can be sealed most effectively by forcing a framework of 2- by 4-inch lumber covered with fiber-reinforced waterproof paper denice strips of heavy felt padding (figs. 10 and bp ouch a sealing can be used many times. Another method is Ficture 9.—Windows sealed on the inside with paper. Cracks about unions of rafters and walls are sealed with plastic cement. (Photograph furnished by W. D. Reed.) to calk the doors with a paste composed of 4 parts of asbestos fiber to 1 part of calcium chloride mixed with a little water. The calcium chloride will absorb enough moisture from the air to keep the paste pliable and thus insure a tight seal. It is a cheap, yet effective, seal- ing material and can be easily removed after the fumigation. 8 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE Machinery that is used to pack, mix, or handle foodstuffs in any way should be opened as completely as possible and all accumulations of materials removed. Most fumigants do not penetrate for more oe FIGURE 10.—Doorway between compartments in modern concrete storage warehouse sealed for fumigation. Framework of 2- by 4-inch lumber, covered with heavy fiber-reinforced waterproof paper, forced against strips of heavy felt padding. The fireproof doors have been rolled back. Note the small door, which also shuts against felt gaskets, for the use of fumigators. A glass window has proved useful in permitting inspection of cperations. FIGURE 11.—Opening to elevator ‘shaft sealed ready for fumigation in Same manner as the doorway in figure 10. In both cases the sealing was done at the Naval Supply Depot, Naval Operating Base, Hampton:Roads, Norfolk, Va. than a few inches into flour, meal, or similar foodstuffs; hence, such accumulations, if left in the machinery, protect insects from the effects of the gas. Accumulations of waste material under or around j : 3 INDUSTRIAL FUMIGATION AGAINST INSECTS 9 machinery, in feed bins, or in any part of the building should also be removed and sold or destroyed before fumigation. Commodities in warehouses or storage rooms should be so arranged as to provide the maximum circulation of the fumigant; large, solid stacks of bagged material should be avoided. In sections that are divided into small compartments or storage rooms, the connecting doors should be opened to allow a proper distribution of the gas. Where sections of a floor are large, as in many metropolitan storages, each section may be fumigated to better advantage as a single unit. DESIRABILITY OF A HIGH TEMPERATURE DURING THE FUMIGATION It is desirable to maintain a fairly high temperature in the build- ing during the fumigation. Insects are not very active at tempera- tures below 60° F., and they become more or less dormant at 50° or below. In the dormant state they are extremely difficult to kill with fumigants. At 75° they are active and their susceptibility to the gases increases as the temperature rises. For best results a tempera- ture of at least 75°, and preferably somewhat higher, should be main- tained throughout the fumigation. EFFECT OF WIND VELOCITY The velocity of the wind during the exposure influences the effective- ness of a fumigation. The fumigation should be conducted preferably when there is no wind, since recent work has shown that in a building of ordinary construction a strong wind will force a large portion of the fumigant away from the windward side and so prevent a uniform distribution of the gas. EFFECT OF LIGHT OR DARKNESS Light and darkness have no appreciable effect upon the results of a fumigation. Although insects are more quickly affected while they are active, entirely satisfactory results follow the application of a fumigant during the day when the insects, such as cockroaches and bedbugs, are chiefly resting in hiding places.. In general, professional fumigators work at times most convenient to the establishment to be fumigated without thought of hght or darkness. In the case of an insect, such as the cockroach, that forages in the dark, more in- dividuals may be killed by a night fumigation if the daytime hiding places are in wall spaces difficult of gas penetration. Usually, how- ever, hiding places of insects in commercial plants are easily pene- trated by fumigants, and the time of day the fumigant is applied is therefore unimportant. CHOICE OF A FUMIGANT In choosing a fumigant several factors must be taken into con- sideration. If the building is modern and very tight, several fumi- gants can be used with success, and a choice can be governed by such items as cost, efficiency, availability, safety, and effect upon the com- modity to be fumigated. If the building is not particularly tight, 4964°—37 2 10 CIRCULAR 369, U. 8S. DEPT. OF AGRICULTURE it will be impossible to maintain a strong concentration of any gas for very long, and a quick-acting gas is the only kind that will be effective. Hydrocyanic acid is the only gas available that will kill quickly. QUANTITY OF FUMIGANT NEEDED The quantity of fumigant to be used will vary according to the length of exposure, the temperature, the tightness of the building, the amount of absorption and adsorption by the commodities to be fumigated and by the walis and floors of the building itself, and the insect to be eradicated. The shorter the exposure, the lower the temperature, the looser the construction of the building, the greater the absorption and adsorption, and the more resistant the insect, the greater must be the dosage. The fumigator must exercise his own judgment in each case. APPLYING THE FUMIGANT The fumigant should be applied in such a way that a maximum concentration will be obtained as quickly as possible. Since most commercial establishments are not airtight, the natural leakage from a building is often great enough to prevent a killing concentration from ever being attained, particularly if it takes considerable time to reach that concentration. From some buildings fumigants escape so rapidly that it is not practical to fumigate them. In buildings that can be fumigated with reasonable expectation of success, the best results are obtained by releasing the entire dosage at the begin- ning of the fumigation. A uniform concentration will be obtained more rapidly if the fumi- gant is distributed equally throughout the building. When using lighter-than-air gases it is not necessary to place the heaviest dosage on the lower floors, since gas concentrations tend to become equalized in all parts of the building shortly after the fumigant is introduced. If the fumigant is not applied from the outside, the fumigating crew should be supplied with gas masks having canisters adapted for the gas that is to be used. Hach operator should be familiar with the entire plan of procedure as well as with his own particular job. One man should be delegated to watch the others and to give aid in case anyone gets into trouble. Help given at the right time will prevent possibly fatal accidents. Before the fumigation is started the building should be thoroughly searched to make sure that no workmen or visitors are inside. Dur- ing the fumigation all entrances to the building should be kept locked and usually guarded by watchmen. Placards warning people to keep out should always be tacked on all doors. VENTILATING THE BUILDING AFTER FUMIGATION After the fumigation the building should be aired out by opening doors and windows. if possible, these should be opened from the outside. If this is not possible, the windows should be opened from the inside by workmen wearimg gas masks and preferably working in pairs to avoid accident. A few windows on the top and bottom floors and on each side of the building should be opened first to INDUSTRIAL FUMIGATION AGAINST INSECTS 11 provide cross ventilation. The men can then go outside and wait until the building is partially aired before completing the work. It is important that the watchmen be instructed to prevent anyone from entering the building while it is being ventilated. A large proportion of the fatalities connected with fumigation have been due to criminal neglect on the part of watchmen. FUMIGATION WITH HYDROCYANIC ACID GAS For the fumigation of large buildings there is no more efficient gas than hydrocyanic acid. It 1s relatively inexpensive, kills with great rapidity, and, al- i though deadly pois- enous, can be han- dled with reasonable safety by experienced men. It can be used in nearly all types of buildings and will not injure most arti- cles of commerce. Hydrocyanic acid gas is commonly pro- duced in one of four ways: (1) By gener- ating it in a barrel, earthenware crock, or other container from a mixture of sodium cyanide, sul- phure -aeqd. anc water—the so-called barrel or pot meth- od; (2) by pumping it into the building or machinery in hq- uid form from cylin- ders—the liquid method: (3) by spreading on the floor of the building an absorbent mate- rial saturated with liquid hydrocyanic Figure 12.—Man wearing gas mask about to lower bag of : sodium cyanide into a barrel containing sulphuric acid : 5 - Bye disc oad and wate If the cyanide is put in a gunny sack, there ° / is no danger of the bottom of the bag breaking and gpill- met uo d; (4) by ing the cyanide. The cyanide should not be dropped into spreading Hin Aging the acid-water mixture; it should be lowered carefully. floor of the building a powder consisting of calcium cyanide, which combines with mois- ture from the air to form hydrocyanic acid gas—the powder method. THE BARREL OR POT METHOD The barrel or pot method of generating hydrocyanic acid gas is so called because the chemicals used are placed together tn a barrel (figs. 12 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE 1 and 12) or some similar container (fig. 13). This method, while more laborious than others, gives excellent results and is the safest for the use of other than professional fumigators. It can be made the cheapest method of fumigation. CHEMICALS REQUIRED Sodium cyanide (96 to 98 percent, containing 54 percent HON), a commercial grade of sulphuric acid (66° B.), and water are the only materials required. Sodium cyanide is a white crystalline sub- stance, which for fu- migation purposes is prepared in egg- shaped lumps weigh- ing approximately 1. to 1 ounce each. It is a violent stomach poison, and can also cause serious poison- ing by being ab- sorbed through open cuts on the hands. For this reason it is best handled with a scoop or shovel or with gloved hands (fig. 14). It can be purchased in 100- pound lots for from 16 to 22 cents per pound,and in smaller lots at a proportion- ally higher price. Pure _— sulphuric acid is a heavy, col- commercial acid used in large-scale fumiga- tion work is slightly discolored, or murky, owing to impurities. It is highly corrosive and will cause injury FIGURE 13.— Crock for the penetration of hydrocyanic acid Tap Mires spattered on gas by the pot method, set in small galvanized-iron tu : £ :: to prevent injury to floors in case the crock cracks. the clothing CL body of the operator or upon the floor. It can be purchased in 11-gallon carboys for about 4 cents per pound. When large quantities of acid are required, a tilting frame will be found convenient in pouring the acid from the carboys. Workmen should learn to pour acid slowly and with cau- tion (fig. 15), for their clothing or shoes will be damaged if a drop of acid falls on them. It is well to have easily accessible a pail of orless liquid, but the 2 INDUSTRIAL FUMIGATION AGAINST INSECTS 13 water in which some washing soda has been dissolved, for quickly washing away droplets of acid that may spatter on face, hands, or clothing. A sulphuric acid pump that can be attached to a carboy is somewhat slower but easier to handle. FORMULA For best results the chemicals should be mixed according to the following formula :* SVGIONTY ETHNIC. Wen Gl Come ere NE St ee eee ne oS pound —_ — “2 SHPO OND SOS GSD SE SRS SRE ire ese repertory ema be te rap ee ar pings! 1s WVU C Teta: ty a tee hd ee eee te ts eS donee. 33 FicurRE 14.—Workmen weighing sodium cyanide for large warehouse fumigation. Man at right shoveling cyanide in 1-ounce lumps from 100+pound case into gunny_ sack held by man in center. Man at left with CRONE WeNeIaoe BOOTE to enter warehouse and place sack beside generator. PROPER ORDER OF PLACING CHEMICALS IN GENERATOR To generate hydrocyanic acid gas by this method, the operator should first pour the water into the generator and then add the acid. If the procedure is reversed, the reaction is so violent that the oper- ator may be dangerously burned by the spattering of the acid-water mixture. The sodium cyanide is not added to the mixture of water and acid until everything is in readiness for the fumigation, as it causes an immediate chemical reaction in which hydrocyanic acid 1Chemical tests indicate that a 1—1%4-2 formula yields more gas than the 1-1144-3 formula here recommended. The smaller quantity of water often results in a crystalliza- tion of the residue which makes the emptying of the containers eaees fumigation more difficult. In general large-scale work the authors have found the 1-1%-3 formula more practical and the results satisfactory. - f 14 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE gas is given off (fig. 16). ‘The pure gas is colorless, but when mixed with steam produced by the chemical reaction it has the appearance of a light bluish smoke. It has an odor resembling that of peach kernels. DOSAGE The dosage is computed on the basis of the quantity of sodium cyanide required. For general mill or factory fumigation where no large quantities of materials are stored, 1 pound of sodium cyanide will produce enough gas to fumigate 1,000 cubic feet of space, if the building is of reasonably tight con- structions, Ui ave building to be fumi- gated is filled with merchandise, the dos- age required will vary according to the nature of the merchandise. Dos- ages have been com- puted for the fumi- gation of the more important commodi- ties and will be dis- cussed in a later sec- tion of this circular. THE GENERATOR For large-scale fu- migations a water- tight 50-gallon wood- en oil barrel (figs. 1, FIGURE 15.—A good illustration of workmen's indifference 12, and 16) 1s the to spattering sulphuric acid. Most industrial plants have nee suitable genera- crews familiar with pouring acid; yet few are particular to avoid spattering and dropping acid. tor to. use. Metal barrels are not satis- factory. Barrels in which paint, glue, molasses, pitch, etc., have been stored should be avoided, for when the acid is added it may eat out these materials from between the staves, thus causing a bar- rel thought to be liquid-tight to leak. Barrels should be cleaned and allowed to stand full of water overnight previous to the day of fumigation. Each barrel will hold a maximum charge of 39 pounds of sodium cyanide, or enough to fumigate about 30,000 cubic feet of space. When it is necessary to fumigate small rooms of a few thousand cubic feet as separate units, earthenware or stone crocks (fig. 13) of appropriate size can be used. Oil barrels sawed in half are used less often. Each barrel generator should be set in a galvanized-iron washtub in which has been placed a pailful of water containing several hand- fuls of washing soda. This precaution provides for catching and aE Pet, Dore krs & hy saniadatnateacsnte nada are INDUSTRIAL FUMIGATION AGAINST INSECTS 15 neutralizing any small quantity of the acid-water mixture that may leak out of the barrel. If three or four bricks are placed in the bottom of the washtubs for the barrels to rest on, the barrels will not become stuck in the tubs. It is much better to have tubs large enough in diameter at the bottom so that the barrels will not come in contact with the sides. If earthenware crocks are used, these also should be set each in a small galvanized tub. It is seldom practical to use crocks of more than 4-gallon capacity. A 38-pound charge of cyanide is the most that can be safely used in a crock of this size without danger of spattering during the evolution of the gas. FIGURE 16.—Seven 50-gallon oil barrels, in tubs, arranged in line near the door of a woollen factory. The sodium cyanide has been dropped into the acid-water mixture. Note gas mixed with steam rising from the barrels. Hach of these barrels had a charge of 25 pounds of sodium cyanide, the battery of seven barrels generating enough gas for 175,000 eubie feet of mill space. HANDLING CYANIDE FOR THE GENERATOR The weighing of cyanide should be delayed as late as possible be- fore the fumigation is begun. The cyanide absorbs moisture, and if it remains in a paper package for a long time before fumigation, the moisture gathering on the lumps of “cyanide will moisten the paper so that when the sack is picked up it may break and dis- charge the cyanide. Where small charges of cyanide are used, as in 4- -gallon crocks, it is best to use two paper sacks, one of which will fit easily inside the other. By wrapping the unoccupied por- tion of the sacks tightly about the cyanide and tying with a string, a compact package is obtained, which can easily be lowered into the acid-water mixture with one hand. If two bags are used, the opera- tor can lower six or eight charges of cyanide into the containers before the acid eats through the ] paper of the charge first dropped, and often he can. be out of the building before any gas is evolved. If the sacks are merely tied close above the cyanide, or twisted, without wrapping, during the reaction the acid-water mixture may 16 CIRCULAR 369, U. 8S. DEPT. OF AGRICULTURE be forced up along the neck of the bag and over the edge of the container. If the cyanide is properly packaged, however, there will be no overflow. When large dosages are used in barrels, sometimes as large as 30 pounds, it 1s safer to place the cyanide in gunny sacks. When charges in. such sacks are lowered into the barrels, gas is evolved at once and the operator must work with dispatch. The evolution of gas can be delayed by wrapping the sack in paper and tying the bundle with cord strong enough so that the bundle can be lifted and lowered into the barrel without danger of breakage. A person vas then lower several charges before gas is discharged from the rst. PLACING THE GENERATORS In the fumigation of large open mills or warehouses, all the generators for one floor can be grouped in a position reasonably close to the exit. It is not necessary to distribute them throughout the room, for the gas is quickly dispersed to all parts of the enclosed space. In fact, where it is impractical to seal off the several floors of a rather small, tight building, excellent results can be obtained | in calm weather by placing all the generators on the lower floor. The gas will quickly diffuse throughout the building. How To GENERATE THE GAS After the mill or warehouse has been prepared for the fumigation and the generators have been placed in their proper positions, the water and acid are measured out and distributed in the generators. The acid can be poured from the carboys into heavy galvanized-iron buckets, which will resist the action of the acid long enough for it to be distributed without accident. If crocks are used for generators, the acid must be poured into the water slowly with a rotating mo- tion, lest the heat developed by the chemical reaction between the acid and water cause the crocks to break. If the crock should crack, the operator must empty it immediately into some handy container provided for such an eventuality. When the water and acid have been mixed, the sodium cyanide, which has previously been weighed into the proper quantities and wrapped, should be lowered carefully into the generators. If sev- eral floors are to be fumigated separately, the cyanide should be dropped first into the generators on the top floor, and then on the next lower floor, and so on to the bottom. Starting with the one farthest from the exit (previously determined), proceed from gen- erator to generator calmly and without delay. Do not retrace steps to a generator accidentally overlooked. If several lines of gener- ators converge at one exit, an operator should be assigned to each line and at a predetermined signal each should start dropping the cyanide in the most distant generator in his line. Since the gas is generated as soon as the acid-water mixture comes in contact with the sodium cyanide, the operators engaged in drop- ping the cyanide should wear gas masks, except for very small jobs where only one or two generators are used. 6 Anise hin’ ok a INDUSTRIAL FUMIGATION AGAINST INSECTS hy EMPTYING THE GENERATORS When the fumigation is finished and the building has been thor- oughly ventilated, the residue must be emptied from the generators. Sometimes the chemical reaction is incomplete because some of the sodium cyanide has not come in contact with the acid-water mixture or because the wrong proportions of the materials have been used. Therefore, when the generator is moved, the contents are shaken up and additional small quantities of gas may be given off. For this reason the operator should breathe as lit- tle as possible or use a gas mask while handling the barrels and should not hold his head over the barrel. The residue, which 1S poisonous, -can be disposed of by dump- ing it down a street drain (fig. 17) or by pouring it into a hole in the ground and covering it with soil. THE LIQUID METHOD Liquid hydrocy- anic acid is a vola- tile, colorless liquid which boils at 79° F. It is marketed in WiecurRE 17.—Men carrying containers from a warehouse cylinders containing see ae eee the residue from a hydrocy- 30 or 75 pounds. On exposure to air it gives off the same gas that is generated by mixing sodium cyanide with sulphuric acid and water. In the hands of an expert fumigator it is an almost ideal fumigant for use in large enclosures. After a building has been prepared for fumigation, the gas is applied entirely from the outside (figs. 18 and 19). The cylinders containing the liquid hydrocyanic acid are lined up near the build- ing, and the fumigant is forced in by coftircced air. A proper distribution of the gas within the building is obtained by means of lines of pressure rubber tubing or metal piping equipped with spray nozzles. A gas mask should be worn or kept close at hand. PIPING THE BUILDING In small enclosures the gas can be distributed through rubber tub- ing, but in large warehouses or mills it is desirable to install a per- manent system of piping. This may be constructed of iron, brass, or copper. The iron piping is the least expensive, but, owing to its 4964°—37_3 18 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE . ; ST = - FIGURE 18.—Fumigating a tobacco warehouse with hydrocyanic acid gas, using the liquid method. The liquid hydrocyanie acid in the cylinder on the scales is being forced, by air pressure generated by a small electrically driven compressor, through the rubber tubing from the cylinder to the piping system installed inside but protruding through the walls. Po te eg he hs» :., FIGURE 19.—Equipment for fumigation of flour mill from loading platform. Note six eylinders of liquid hydrocyanie acid, two electric motors, outlets in the wall leading to six piping systems to carry fumigant to six separate compartments, floors, or pipe lines within. The two motors are forcing, by air pressure, the liquid hydrocyanic acid in two of the cylinders through rubber hose into two of the systems of copper piping within. Note placard on door warning of danger. 4 INDUSTRIAL FUMIGATION AGAINST INSECTS 19 tendency to rust and cause clogging of the spray nozzles, it 1s rarely used. Either brass or copper tubing is recommended. A flexible copper tubing three-eighths inch in diameter (fig. 20) costs about 6 cents a foot. Since it can be readily bent, elbow fittings are unneces- sary, and compression couplings can be used, except at the main inlet, where the cylinders are connected. In large buildings, where there are several floors and numerous branch lines must be used, each floor should be provided with a separate riser, which should be of larger ieDlomudven se NOI OE) A moazele Chet. 21) should be provided for every 15,000 to 25,000 cubic feet of space. It is custo- mary to use from 10 to 18 nozzles to a riser, but the latter number should not be exceeded. Most buildings can be piped with copper tubing at a cost of about 10 to 13 cents per 1,000 cubic feet of space. Brass tub- ing costs about two and one-half times as much as copper. The piping system. should be so ar- ranged that the gas Figure 20,—Installation of %g-inch copper piping for in- pressure will be ap- troduc ection of liquid hydrocyanic acid. ns piping, being exible and easily cut with a saw, as indicated, can be proximately the same run along side walls and out along rafters, or to any at all nozZles, thus point where it seems best to install the spray nozzles. insuring an even dis- tribution. Each riser is connected to a special inlet pipe leading through the outside wall of the building to the cylinders of gas. Pip- ing plans are usually made by the fumigating company after it has made a survey of the building. Should blueprints or rough sketches and measurements be forwarded for making piping plans, special attention should be given to offsets and whole or part partitions. Any other special conditions, such as heavily infested machinery, rows of packing machines, or other places of heavy infestation, should be noted in order that an extra nozzle may be added if it is thought desirable. APPLYING THE GAS Each cylinder of liquid hydrocyanic acid is supplied with an inlet valve and an outlet valve. The outlet valve is attached to a steel tube connected with the bottom of the cylinder. The inlet valve 0) CIRCULAR 369, U. S. DEPT. OF AGRICULTURE leads directly into the top of the cylinder, and through it air is pumped, by means of a small compressor (figs. 18 and 19), until a pressure of about 100 pounds is obtained. The outlet valve, which has previously beeen connected with the inlet pipe to the building, is then opened and the gas is forced in. The pressure must be main- tained until the liquid 1 is blown through the pipes into the space to be fumigated. As soon as the required quantity of liquid hydrocyanic acid has been forced into the building, the pipe lines are blown clear and the inlet tubes capped. The time needed to pump the contents of a 75- ‘pound cylinder into a building is approxi- mately 7 minutes. SAFETY PRECAUTIONS At the conclusion of the fumigation and after the building has been well ventilated, the spray nozzles should be re- moved and cleaned for storage and the pipes capped. In removing these nozzles, care must be taken to avoid acci- dents from the small quantities of liquid hy- drocyanic acid that some- times remain in the pipes after a fumigation. The operator should never stand directly in front of or beneath a_ spray nozzle that is being re- moved. It is best to use a gas Figure 21.—Various attachments for spray nozzles mask in this work. The With lmuid Kedrowanie adds ee presencesot lquidehaeee: eyanic acid behind a noz- zle that is being unscrewed is usually revealed by a well-defined cool- ing sensation and sometimes by a slight odor. Special pressure noz- gles are now on the market which close automatically when the pres- sure 1s removed; hence they do not clog and need not be removed. In fumigating with liquid hydrocyanic acid, there is always some danger that the rubber connecting hose may burst under the pressure, showering the operator with the deadly fluid. It is therefore a wise precaution to check the rubber hose and all connections thor- Laat Pepsi 0 5 ee Re ee ee yen . / INS EOS TE hire POR e+ a = INDUSTRIAL FUMIGATION AGAINST INSECTS 21 oughly before turning on the gas and to wear a gas mask while manipulating the valves of the cylinder. THE DISCOID METHOD For the fumigation of warehouses that are divided into sections, of mills containing machinery that cannot be easily opened up, or of apartment buildings, etc., the use of some form of solid from which hydrocyanic acid g eas can be produced is often desirable, since it does away with the necessity for an elaborate piping system or for crock or barrel generators. FIGURE 22.—Lobby of apartment house being fumigated with hydrocyanie acid gas generated by the discoid method, showing round white wafers distributed over the paper runner and the empty cans from which they have been shaken. These wafers are wet when distributed, but after the evolution of the gas they become dry and harmless. There are two types of such solids now on the market. One of these consists of liquid hydrocyanic acid absorbed in some inert. material, from which it evaporates on exposure to air. This inert material is pressed into waferlike discoids each containing approxi- mately one-half ounce of liquid hydrocyanic acid (fig. 22). ‘These discoids are marketed in tightly sealed cans of various sizes and sold on the basis of the net content of hydrocyanic acid. The other type of solid is calcium cyanide, and the hydrocyanic acid is produced by chemical reaction with the moisture in the air. Its use will be dis- cussed under the powder method. 92 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE APPLYING THE DISCOIDS When large quantities of discoids are used, especially in hot weather, it is advisable to chill the cans before fumigating. This will greatly retard the generation of the gas and thus increase the safety of operation, If solid carbon dioxide is available, a liberal quantity thrown over the tops of the cans in each opened case a few hours before fumigating will chill the discoids. Solid carbon dioxide can usually be purchased for from 38 to 5 cents per pound. Placing cans of discoids in cold storage will have the same effect. The proper number of cans of discoids should be placed on each floor to be fumigated, and the distri- bution of the fumigant should be started on the top floor, always from a predetermined point and approaching the exit. The cans are opened with a specially devised can opener that makes a clean cut close to the rim (fig. 23). If several operators are engaged in the work, one can open the cans while the others scatter the discoids over the floor or among the machinery. The men should take turns opening the cans, so that one man will not be ex- posed too long to the heavy concentrations near the newly opened cans. Discoids should not be ? placed directly on painted FicurE 23.—Man, protected by gas mask, removing OF varnished floors or Hated with liguid byduocyanic acid. |. 2... woodwork, for the lugasd hydrocyanic acid is likely to injure the finish. Two or three thicknesses of newspaper or wrap- ping paper will provide adequate protection against any liquid that may ooze from the discoids. When discoids are used, the fumigators are exposed to the gas while they are opening the cans and distributing the contents. Good gas masks are necessary and will prevent them from breathing poi- sonous fumes, but there is also some danger from the direct absorp- tion of hydrocyanic acid gas through the skin. Willams? has esti- 2 WILLIAMS, C. L. FUMIGANTS. Pub. Health Repts. [U. S.] 46: 1018. 1981. a 4 é ; sid a ty, Ss nll RY ats WP Nie “tics SGP RIAA WEEE oI. i ChE MT Ee , a Np bine =“ — - ° INDUSTRIAL FUMIGATION AGAINST INSECTS 293 mated that a man protected by a good gas mask can remain in air containing 2 ounces of hydrocyanic acid gas per 1,000 cubic feet for half an hour without being affected; in a concentration of 4 ounces per 1,000 cubic feet this time should be reduced to 15 minutes, and in one of 8 ounces to 5 minutes. The same author calculates that, m distributing discoids at the rate of 8 ounces of hydrocyanic acid per 1,000 cubic “feet, a fumigator will be actually exposed for the greater part of the time to from 1 to 2 ounces per 1,000 cubic feet. ‘Allow- ance is made for the fact that the fumigator 1S constantly moving away from the discoids and that the full quantity of the gas is not given off immediately. If the discoids are chilled before being used, the concentration to which the fumigator is exposed will be less From the foregoing data it is evident that, where large quantities of discoids are used, the fumigating crew must be large enough so that the distribution of the fumigant will be speedy and no one man is exposed to the gas for a dangerously long period. ‘The use of this material is not recommended for any but professional fumigators. DISPOSING OF SPENT DISCOIDS When the fumigation is finished and the building has been well ventilated, the spent discoids and the empty cans can be gathered up and thrown away. At the end of a 24-hour fumigation the discoids will retain not more than a trace of hydrocyanic acid. THE POWDER METHOD Calcium cyanide in dust form is used in much the same way as the discoids. On exposure to the air the powder absorbs moisture and a chemical reaction takes place by which hydrocyanic¢ acid gas is given off. APPLYING THE POWDER The required number of cans of calcium cyanide are distributed throughout the building. They are then opened and the contents scattered over the floor in a layer not more than haif an inch thick. To facilitate removal of the dust after the fumigation, it may be scattered on strips of paper previously laid on the floor, although’ it 1s sometimes placed directly upon the floor (fig. 24). Hach can of fumigant is equipped with a special perforated top, which the fumi- ator puts in place of the friction top when he is ready to use it. Inasmuch as the gas is given off very rapidly after the dust is exposed to the air, the fumigator should wear a gas mask while dis- tributing it. As in the case of the discoids, he should begin distribut- ing the dust at the point farthest from the exit, so that he will be working away from the gas that is being given off. After the fumigation, the paper on which the dust is spread can be rolled up and thrown away, or the dust can be swept from the floor and placed in containers, to be disposed of immediately. The residue, which is mostly calcium hydroxide, is likely to absorb some of the hydrocyanic acid from the air; hence it is advisable to dispose of it outside the building, where small quantities of escaping hydro- cyanic acid gas will harm no one. After all the hydrocyanic acid has been given off, the residue 1s nonpoisonous. 24 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE As the dust may be blown about while the building is being ven- tilated, it should be removed as soon as possible. To obviate this difficulty, as well as for other reasons, the gas is sometimes liberated in a special apparatus (fig. 41). Air is forced by a small motor into a rubberized sack containing the calcium cyanide dust, which is kept agitated until all the hydrocyanic acid gas is liberated. The gas enters the space to be fumigated through a filtering device, which frees it of the dust. FIGURE 24.—Warehouse being fumigated with hydrocyanic acid gas by the powder method. Calcium cyanide in dust form is spread on the floor, usually from tin cans with perforated covers. THE DOSAGE To figure the quantity of calcium cyanide needed for a fumigation, it is necessary to know the percentage of available hydrocyanic acid it contains. This percentage will be found on the label of the can. If, for example, the dust contains 50 percent of available hydrocyanic acid, 1 pound will give off as much gas as 8 ounces of liquid hydro- cyanic acid or 1 pound of sodium cyanide. Calcium cyanide ranges in price from $1.60 per pound in 1-pound cans to $1.20 per pound in 25-pound cans. FUMIGATION WITH CHLOROPICRIN Chloropicrin, although not so popular as hydrocyanic acid, is sometimes used as a general fumigant for mills and warehouses. It is a colorless or slightly yellowish liquid, a little more than one and a half times as heavy as water. It has a boiling point of 233.6° F., and on exposure to air evaporates slowly, forming a mixture of air and chloropicrin vapor that is 1.1458 times as heavy as air at the same temperature and pressure (77° F., 29.9 inches). It can be purchased in cylinders of from 1 to 100 pounds’ capacity at a_cost of $1.20 per pound for 1-pound cylinders down to 85 cents per pound in 100-pound lots on contract. The gas is nonexplosive and nonin- flammable as ordinarily used, is very toxic to insects and also to L829 SAG AER EME NS eg i aaa a i a ih 6 lee Seg | INDUSTRIAL FUMIGATION AGAINST INSECTS 25 man, and has an extremely irritating effect upon the eyes and respira- tory passages of man. This last characteristic insures against the possibility of anyone accidentally entering a building filled with gas. A gas mask equipped with a canister especially designed for the pur- pose must be worn when fumigating with chloropicrin. . There are several methods of applying chloropicrin as a general mill or warehouse fumigant. The simplest of them is to draw the required quantity of liquid from the cylinder in which it is mar- keted into a sprinkling can and sprinkle it over the floor or commod- ity or into the machinery. It should not be apphed directly on painted or varnished surfaces. Where there are several stories to a building, each floor should be sealed off from the others. Owing to the rather high boiling point of chloropicrin and conse- quent slow rate of evaporation, it is sometimes desirable to hasten the process by applying the liquid in the form of a spray or fine mist, or by using a mixture of equal parts of chloropicrin and see tetrachloride or trichloroethylene. At temperatures above 70° F., however, satisfactory results can be obtained by merely applying the straight chloropicri in with a sprinkling can, In mills that are equipped with machinery for handling food- stuffs, it may be desirable to apply a portion of the chloropicrin directly into the machinery where the heaviest infestation is likely to be found. In such cases the fumigant can be applied with a com- bination of sprinkling cans, sprinkler bottles, sprayers, ladles, or tin measuring cups. One-pound “automatic” cylinders of chloropicrin charged with carbon dioxide are sometimes used for treating machinery. They are supplied with a short length of hose ending ‘with a spray nozzle. The nozzles are inserted into holes bored into the machinery, and the gas is released by opening a valve on the cylinder. The pres- sure of the carbon dioxide expels the chloropicrin in a fine mist. An objectionable feature of chloropicrin is that considerable time is required to ventilate a building after a fumigation. Because it does not evaporate rapidly, it clings to fumigated commodities with great tenacity. FUMIGATION WITH ETHYLENE OXIDE-CARBON DIOXIDE MIXTURE Warehouses and storage rooms that are of modern tight construc- tion can be successfully fumigated with a mixture of ethylene oxide ~and carbon dioxide. This mixture is put up in cylinders in the pro- portion of 1 part by weight of ethylene oxide to 9 parts of carbon dioxide. It is noninflammable, and is not sufficiently toxic to human beings to make its application unpleasant or dangerous. It leaves no obnoxious odor or poisonous residue on the commodity fumi- gated. The mixture is sold in 30- and 60-pound cylinders at prices ranging from 14.5 to 16 cents per pound, f. o. b. the factory. The ‘application of the ethylene oxide-carbon dioxide mixture is exceedingly simple. The requisite number of cylinders are placed in the room to be fumigated and the valves opened. The pressure of the carbon dioxide automatically discharges the contents of the cylinders in the form of a very fine mist, which vaporizes at once 4964°-—37——__4 26 CIRCULAR 369, U. 8. DEPT. OF AGRICULTURE (fig. 25). A cylinder of the mixture will empty itself in about 5 minutes after the valve has been opened wide. When the valves are opened wide, the force of the escaping gas often causes the cylinders to topple over. To avoid this, the cylin- ders can be lashed to the walls of any stationary object, or several cylinders can be lashed together with the discharge vents pointing in opposite directions. Unless a large number of cylinders are used in a fumigation, the valves can be opened without the use of a gas mask, although it is not advisable to stay in a strong concentration of the gas for any appreciable length of time. Before starting the fumigation it is - well to see if the valves on all the cylinders can be opened easily by hand; any that are stuck should be loosened with a wrench. FIGURE 25.—Cylinder of ethylene oxide-carbon dioxide mixture being emptied automati- eally by the pressure of carbon dioxide within. Tf desirable, a storage room can be piped in the same manner as for liquid hydrocyanic acid, and the ethylene oxide-carbon dioxide released into the room from the outside. The cylinders are all equipped with fittings that can be connected with the piping system (fig, 26). The Ue es quantity of this mixture that should be drawn from a cylinder at one time is 10 pounds, since it 1s difficult to withdraw uniform mixtures of carbon dioxide and other fumigants in smaller quantities. When portions of cylinders of mixed gases are used, it is well to follow the instructions of the manufacturers. Where the floors are painted or varnished, the cylinders should be placed in shallow pans or on several thicknesses of newspaper, to prevent damage in case the liquid should run down the sides of the eylinder. This mixture is very effective in rooms that are nearly airtight, but it should not be used in rooms that are loosely constructed. After the fumigation and ventilation all that is necessary is to roll the empty cylinders out of the room and return them to the owner. 9 INDUSTRIAL FUMIGATION AGAINST INSECTS 7 FUMIGATION WITH METHYL BROMIDE-CARBON DIOXIDE MIXTURES A mixture of methyl bromide and carbon dioxide has recently been placed on the market as a fumigant for use in vacuum chambers, at- mospheric vaults, and tight storage rooms. It is sold in steel pr essure eylinders containing 50 “pounds at 15 cents, f. o. b. shipping point. Methyl bromide is nonintlammable and has a boiling point of 40.1° F. It is a gas at ordinary room temperatures. It is similar FicurRE 26.—Battery of 10 cylinders of ethylene oxide-carbon dioxide mixture attached to manifold, heaters, and distributing pipes connecting with storage vaults (not shown) in room. In lower background is a 6- by 8- by 10-foot metal fumigation vault, which opens into the room beyond. to ethylene oxide in that the killing effect is delayed. Methyl bromide is poisonous to human beings,® since after absorption by the body it breaks down forming methanol, which continues to accumulate in the body as long as the exposure persists. Severe poisoning by methanol results after prolonged exposure to concentrations of methyl bromide too small to exhibit an anesthetic action; hence workmen should not be exposed to appreciable concentrations of the gas. The dosages recommended vary with the commodity to be fumi- gated, but under ordinary atmospheric conditions the usual dosage is 15 to 20 pounds of the mixture per 1,000 cubic feet for an exposure of 24 hours. The fumigant is discharged into the atmospheric fumigation cham- ber or storage room in the form of a slush or snow or as a gas. It ®’ HENDERSON, Y., and HaGGARD, H. W. NOXIOUS GASES, p. 159. New York. 1927. pres CIRCULAR 369, U. S. DEPT. OF AGRICULTURE is more quickly effective if it is first passed through a vaporizer and introduced as a gas, as is the practice in vacuum fumigation. FUMIGATION WITH METHYL FORMATE-CARBON DIOXIDE MIXTURES Warehouses and storage rooms that are thoroughly modern in construction can be fumigated with mixtures of methyl formate and carbon dioxide. Ordinarily these mixtures are used cnly in special fumigation vaults. The value of methyl formate as a fumigant was first established by the experimental work of this Department. Alone, its vapors are explosive and inflammable in the presence of fire in any form; hence, mixtures with carbon dioxide have been developed, the vapors of which are entirely free from the fire and explosion hazard. The methyl formate-carbon dioxide mixtures are sold at from 10 to 35 cents per pound, depending upon the size of the cylinders and the percentage of methyl formate used. They can be obtained in steel pressure cylinders containing a net weight of 5, 8, 25, 50, or 60 pounds. When used in connection with vault fumigation, the cylin- der is set on platform scales close to the vault wall, through which the desired dosage is discharged. The method of application is the same as that recommended for the methyl bromide-carbon dioxide mixture. The vapors seem to be harmless to food and other commodities thus far treated, and they are only slightly toxic to man as he ordi- narily comes in contact with them in fumigation work. The recom- mended dosage is 28 pounds per 1,000 cubic feet of empty space, with an. exposure of from 12 to 24 hours. Several mixtures have been offered to the public, but one containing about 15 percent of the methyl formate seems to be the most effective and safe. This fumi- gating mixture is similar to the ethylene oxide-carbon dioxide mix- ture in the manner in which it is marketed and used. VAULT FUMIGATION Many establishments have use for a small fumigation vault for the treatment of incoming raw materials, returned goods, outgoing prod- ucts, etc. Such a vault may be constructed of any material that can be made gastight or reasonably so. Several types of metal vaults (fig. 27) can be purchased knocked down ready for assembling. ‘These are excellent in every way. Highly satisfactory vaults can be constructed of concrete, brick, or hollow tile. The brick (fig. 28) and hollow-tile (fig. 29) vaults should be finished inside with a layer of Keen’s cement and one or two coats of paint. Wooden vaults with a metal lining are also popular. It is possible to purchase 14-gage sheet metal cut up into sections for constructing a vault 8 by 10 by 12 feet. When welded together, the sections form an excellent gastight lining. The cheapest type of vault is made of wood. A useful vault can be constructed of two layers of 2-inch standard flooring separated by a layer of heavy roofing paper. If the edges of each board are painted with heavy white-lead paint just before the tongue and groove are forced tightly together, the walls are even tighter. The PR (TS. as el INDUSTRIAL’ FUMIGATION AGAINST INSECTS 99 floor, walls, and roof should be of the same tight construction. The interior should be given two or three coats of any good paint. An aluminum paint is sometimes used to advantage. All types of vaults should be equipped with a refrigerator or safe type of door, well gasketed to make it gastight. A ventilating system capable of quickly removing the fumigant from the vault after the fumigation is essential. If ‘the vault is set up inside a building, the ventilating stack must extend outside the building and prefer ably above the roof. It is sometimes desirable to install an electrical heating unit, con- trolled by a thermostat, so that a constant high temperature can be maintained throughout the fumigation. The heating unit should not be operated, however, while inflammable fumigants are being used. FicurE 27.—Two types of metal vaults such as can be purchased or built according to space and commodity need. These vauits are used for treating the day’s arrival of fur coats offered for summer storage. After an overnight fumigation in these vaults the furs are removed to large permanent storage vaults. For applying the fumigant several different methods can be used. For heavier-than-air gases a shallow evaporating pan or trough should be installed near the ceiling of the vault, with a feed pipe ex- tending outside (fig. 29). The fumigant can then be run into the evaporating pan by gravity or compressed air. If liquid hydro- eyanic acid or any of the commercial mixtures is to be used, a short piping system with one or more spray nozzles can be installed (figs. BOO. ande26,) USE OF BU MIGANES SUITABLE ALSO FOR LARGE SPACES Hy drocyanic acid, chloropicrin, and mixtures of carbon dioxide with ethylene oxide, methyl bromide, ‘and methyl formate are all suitable for vault fumigation, and they’ can be used in the manner described for the fumigation of large spaces. The method selected for gener- ating hydrocyanic acid will cpnend largely upon the preference of the operator. Any. of the _preyiously, described ‘methods is suitable. wheel 30 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE FIGURE 28.—Two outdoor fumigation vaults under ene roof, built of brick, finished on the inside with Keen’s cement, and equipped with doors shutting against rubber gaskets to prevent gas leakage. Note ventilators in roof to aid in ventilation when lighter-than-air gas is used. (Photograph by Perez Simmons.) FIGURE 29.—Outdoor structure built for fumigation of dried fruits. It is made of = hollow tile, plastered on the inside with Keen’s cement, and equipped with a re- = frigerator-type door. Note funnel-shaped openings above the door, through which a liquid fumigant can be poured into evaporating trays suspended from the ceiling of the vault. (Photograph by Perez Simmons.) If calcium cyanide is used, it can be sprinkled in a thin layer on a strip of paper laid on the ‘floor or on shelves built for the purpose. Chloropicrin can be applied by pouring the dosage into the evaporat- ing pan or by forcing it in through a piping system with com- pressed air. The mixtures of ethylene oxide, methyl bromide, and INDUSTRIAL FUMIGATION AGAINST INSECTS 31 methyl formate with carbon dioxide are applied through a piping system and can be administered by connecting the cylinder to the system (fig. 26) and opening the valve. If the cylinder is placed ona platform scale, it is an easy matter to let in the quantity desired. USE OF OTHER FUMIGANTS Various other fumigants, not suitable for warehouse fumigation, can also be used successfully for vault fumigation. These are car- bon disulphide, ethylene oxide, ethylene dichloride-carbon tetrachlo- ride, and carbon tetrachloride. CARBON DISULPHIDE Carbon disulphide is a colorless, volatile liquid, which boils at 114.8° F. On exposure to air it evaporates, forming a heavy vapor that is very toxic to insects. It is applied by pouring the liquid into the evaporating pan of a vault at the rate of about 5 pounds per 1,000 cubic feet of space. If the vault is not tight or if highly absorbent commodities are being treated, the dosage should be increased proportionately. It is not uncommon to use from 20 to 80 pounds per 1,000 cubic feet. The vapors of carbon disulphide, when mixed with air in certain proportions, are highly inflammable and explosive; hence this fum1- gant should be used only where the fumigation vault is isolated from other buildings, and where the fire hazard can be controlled. Mixtures of carbon disulphide with other chemicals, such as carbon tetrachloride and sulphur dioxide, for the purpose of reducing the fire hazard are now on the market. Although not absolutely nonin- flammable, they can be used with comparative safety. Their efficacy 1s directly proportional to the carbon disulphide content, and they should be used accordingly. The vapors of carbon disulphide are poisonous to human beings if breathed for an extended period. Exposure to light concentrations may induce a feeling of giddiness, which, however, will quickly pass off on coming out into the fresh air. Small quantities of carbon disulphide can be handled without danger by the ordinary person, although persons having any heart trouble should take little part in its ‘application. Carbon disulphide ranges in cost from about 6 cents a pound in 500-pound lots to 80 cents a pound in 1-pound lots. CARBON TETRACHLORIDE Carbon tetrachloride is a colorless, volatile liquid having a boiling point of 170° F. Its vapors are noninflammable, and therefore it 1s sometimes recommended as a fumigant in place of carbon disul- phide. It is not very effective when used alone against insects that infest stored products and should be chosen only when no other fumigant will do. Its chief use is for mixing with more toxic fumigants to reduce the fire hazard. To be at all effective, it must be used at a temperature of 75° F. or higher, and at the vate of at least 30 pounds per 1,000 cubic feet of space. It is applied by pouring it into the evaporating pan of the 39 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE vault. The vapors of carbon tetrachloride have an anesthetic effect when breathed by man. Although they are not quickly toxic, it is not safe to remain for any length of time in a strong concentration of the gas. The cost of carbon tetrachloride ranges from about 5.8 cents per pound in large quantities to 10 cents per pound in small lots. ETHYLENE DICHLORIDE Ethylene dichloride is a colorless liquid with an odor similar to that of chloroform. It has a boiling point of 183.2° F., and on ex- posure to air it evaporates. The mixture of air with ethylene di- chloride vapor is 1.2552 times as heavy as air at the same Meme and pressure (77° F., 29.9 inches). Tt is an effective “fumigant in gastight vaults, but owing to its high boiling point it should be used at a temper ature of at least 70° F. and preferably somewhat higher. The vapors of ethylene dichloride are shghtly inflammable. It is therefore customary to use this fumigant in combination with some noninflammable chemical, such as carbon tetrachloride or trichloro- ethylene. A mixture of 3 volumes of ethylene dichloride with 1 vol- ume of carbon tetrachloride or trichloroethylene is free from fire hazard under ordinary conditions, and is an effective fumigant when used at the rate of 14 pounds per 1,000 cubic feet of space, unless the vault is filled with absorbent material, when a heavier dosage is required. This fumigant is apphed by pouring it or forcing it under pres- sure into the evaporating pan of the vault. A small fan blowing on the surface of the liquid insures a more rapid vaporization of the fumigant and hastens its killing action. The vapors of ethylene dichloride have an anesthetic effect upon man, and although it is safe to use in small quantities, one should not be exposed to a heavy concentration of the gas for more than a very brief period without a gas mask. The mixture of ethylene dichloride and carbon tetrachloride or trichloroethylene has no corrosive action on metals or any bleaching or staining action on textiles of any sort. It is suitable for treat- ing grains and seed, but should not be used for foodstuffs with a high fat content, for they are likely to retain a disagreeable odor and taste after fumigation. Ethylene dichlor ide can be purchased separately or ilready mixed with carbon tetrachloride or trichloroethylene. The mixture of 75-percent ethylene dichloride and 25-percent car- bon tetrachloride is priced at 6.44 cents a pound in nonreturnable 55-gallon drums which contain 590 pounds net, f. o. b. the factory, with freight allowance to destinations east of the Rocky, Mountains. The corresponding price west of the Rocky Mountains is 6.94 cents a pound. In smaller quantities the price is higher. ETHYLENE OXIDE Ethylene oxide is a colorless gas at ordinary temperatures, but below 50° F. it is a colorless liquid. It has a boiling point of about 57.2°, and therefore it can be used with success at temperatures con- siderably below 70°. « INDUSTRIAL FUMIGATION AGAINST INSECTS 33 The concentrated vapor of ethylene oxide is inflammable, but con- centrations up to 314 pounds per 1,000 cubic feet of space are non- explosive and noninflammable. A dosage of 2 pounds per 1,000 cubic feet will give satisfactory results in a tight vault, with an exposure of from 10 to 20 hours. The liquid, which is sold in cylinders, can be drawn off into a measur- ing container and poured into the evaporating pan of the vault. Owing to its extreme volatility, it should not be drawn from the cylinder until the fumigation chamber is ready for the charge. Ethylene oxide gas 1s not injurious to fumigated commodities, and no obnoxious odor or poisonous residue is left upon them. The gas is not highly toxic to man and can be handled in small quan- tities without danger or discomfort. Nevertheless, the operator should avoid breathing the fumes for any length of time and should not enter a heavy concentration without wearing a gas mask. If ethylene oxide is used alone, it is advisable not to operate an electric fan inside the vault, lest an inflammable concentration of the gas has been accidentally obtained. Ethylene oxide can be purchased in cylinders containing 314, 1814, 75, or 195 pounds. In the two largest containers this fumigant costs 42 cents a pound, f. o. b. the factory. When delivered from ware- houses, the price 1s 46 cents a pound east, and 48 cents west, of the Rocky Mountains, f. 0. b. warehouses. BIN FUMIGATION Bins used for the storage of foodstuffs, yarn, hosiery, etc., fre- quently need to be fumigated. For this purpose any of the heavier- than-air gases, such as carbon disulphide, chloropicrin, ethylene oxide, or ethylene dichloride-carbon tetrachloride mixture, can be used, provided it is suitable for treating the commodity stored in the bin. , The fumigant should be sprinkled evenly over the surface of the contents of the bin, and the bin should then be covered as tightly as possible. As the fumigant evaporates, the vapor, being heavier than air, gradually penetrates the material from the top to the bottom. The quantity of fumigant needed will depend upon the tightness of construction of the bin, the type of material to be fumigated, and the fumigant being used. Bins are seldom so tight as fumigation vaults; hence larger dosages are necessary. Since it is difficult to obtain uniform penetration of fumigants beyond certain depths in bins, it is often desirable to apply the fumigant in separate portions as the bins are filled. VACUUM FUMIGATION In vacuum fumigation commodities are placed in a gastight steel chamber, and a large proportion of the air is removed and replaced with a gas lethal to insects. By this method immediate penetration of commodities by the gas is obtained and the susceptibility of the insects is increased by the reduction of the oxygen content of the chamber. This permits smaller dosages and shorter exposures than 34 CIRCULAR 369, U. 8S. DEPT. OF AGRICULTURE under atmospheric conditions. With many commodities the period of exposure may be reduced to as short a time as 1 hour, a feature that has an appeal in industries where speed is essential, as in the handling of foodstuffs and similar commodities. In addition to reducing the dosage and length of exposure, this method of fumigation offers further advantages. At the end of a fumigation the ‘removal of the fumigant can be speeded by the process known as air washing, which consists in drawing a high vacuum and breaking it with air. Furthermore, workmen are not exposed to such heavy concentrations of gas while unloading a fumigation chamber. EQUIPMENT Vacuum chambers are either cylindrical (figs. 80, 31, and 32) or rectangular (fig. 33). They are made in all sizes, from laboratory outfits with a capacity of about 1 cubic foot up to those capable of holding one or more carload lots. The size of the chamber will depend on the type and quantity of material to be fumigated and the space available for it in the factory. Some firms prefer to have two chambers that can be operated with one set of equipment. While one chamber is under fumigation, the other can be loaded or un- loaded and the fumigation crew kept continuously busy. The tanks are usually installed so that small trucks or factory skids can be run into them. If the vacuum chamber is equipped with a door at each end, the trucks can be run in at one end and out the other, so that the fumigated products will not interfere with the next load. In some factories one end of the chamber opens into the receiving room and the other end into the general storage room. Raw materials likely to be infested are then fumigated before they are placed in the general storage rooms. The doors of the vacuum tank should be so balanced and hung that they can be quickly opened and closed by one man. The gaskets should be durable and at the same time provide a gastight seal, The efficiency of a tank depends largely on its freedom from leaks. A well-built tank should hold a vacuum without perceptible loss throughout the average fumigation period. Each installation requires a vacuum pump capable of drawing a 28-inch vacuum in 10 minutes or less. Recent work has demonstrated that it is advantageous to intro- duce the fumigant into all parts of the tank at once instead of through one inlet. Rectangular tanks are now being supplied with multiple gas inlets spaced evenly along the four longitudinal sides. It has also been demonstrated that by circulating the gas in a tank the dosage can be reduced 25 percent by virtue of the better distribution obtained. By means of a bypass from the exhaust to the multiple gas-inlet system the vacuum pump can be utilized to circulate the gas in the tank. This feature is now standard equipment with some tanks. The use of a vaporizer in connection with a vacuum chamber in- creases its efficiency by insuring the entrance of the fumigant in a gaseous state. The most common type of vaporizer consists of a steel tank in which steam is generated by means of electric heating elements, A copper coil, thr ough which the fumigant is conducted. 30 TS AINST INSEC AG TION RIAL FUMIGA NDUST I I0y SJUSTIIRIZW “yuR Jo do} uo -19MOd oY} ‘Seqn} Jo spue wWOAsy ABMB S Ur jJooJ § Aq SUOT Joey EO ST inqye ‘UOlWestuiny 30d IOJBINWMINIe [wVotApuT[AD oy} pueP ‘a UISUIMS JYSII 1B SLOOP 910N Yue) You “vVulorey YON UL JUSUIYSI[GV n Ss 9 0DDBQO] 03 1B | ® UE poT[e}sut IpIs o11soddo oy} UO 91¥ JURSTIUIN oY} SULNpOAUT AOp d1]BuI0jNB oy) ‘duind wannodeVAa [NF Od9Rq01 YSTyIny, Jo spunod QoOO'sF JO PBOT B SoyVI puev AO]IUIVIP ‘yuetd uonestuny WNndeA YURI-OM} YW—OS AUN Iodure} PUB WINNDVA SBSUIPIODIAI IOJ Sadr E 36 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE runs through this steam-heated tank and is so designed that the fumigant is in gaseous form by the time it reaches the vacuum chamber. If carbon disulphide is used, a specially designed vapor- izer is required, since it must be mixed with carbon dioxide before it is admitted to the fumigating chamber. In some modern vacuum outfits an accumulator tank is utilized to vaporize and heat the fumigant before drawing it into the vacuum chamber. It consists of a tank with a heating coil into which the dosage is drawn, and in which it can be held until ready for use. SS AAS = : FIGURE 31.—End view of vacuum equipment shown in figure 30, Tank at left closed and under fumigation. Tank at right nearly loaded with 43,000 pounds of Turkish tobacco. These tanks will treat all incoming tobacco placed in this storage establish- ment. Note end of cylindrical accumulator on top of tank at right. . Hydrocyanic acid, chloropicrin, and mixtures of carbon dioxide with ethylene oxide, methyl bromide, methyl formate, and carbon di- sulphide are used in vacuum fumigation. The dosage required de- pends on the type and quantity of the commodity to be fumigated, its temperature, and the length of exposure. PROCEDURE The commodity to be fumigated is loaded into the vacuum tank, the doors are closed, and air is removed until the vacuum gage regis- ters 28 or 29 inches. The proper dosage of fumigant is then admitted through the vaporizer or accumulator. If the tank is equipped with multiple gas inlets and a gas-circu- lating system, the fumigant should be pumped from the accumulator tank into the vacuum tank through the circulating system. When all the fumigant is in the tank, the valve to the accumulator tank Ce ae INDUSTRIAL FUMIGATION AGAINST INSECTS 37 should be closed and the necessary valve adjustments made to allow the gas to be circulated in the vacuum tank. The gas should be cir- culated for 15 minutes. By holding the remaining vacuum without change for the duration of the fumigation, better results are ob- tained than by breaking the vacuum with air. If the instrument panel is equipped with a recording device, a chart record (fig. 34) can be made of each fumigation for future reference. FIGURE 32.—Portion of vacuum fumigator installed in a large candy establishment. Note vacuum pump in left foreground; cylindrical accumulator on tank; gages for auto- matically recording pressure, vacuum, and temperature; and cylinder of the ethylene oxide-carbon dioxide mixture in front of operator. Cylinders of methyl formate-carbon . dioxide and methyl! bromide-carbon dioxide mixtures are attached in the same manner. The dosage is usually measured by weighing the fumigant into the tank or vaporizer, by measuring it volumetrically, or by dropping the vacuum a given number of inches with the fumigant. The first two methods are accurate. The third method cannot be used indis- criminately, since with a given.quantity of gas the drop in vacuum will vary both with the quantity and the type of commodity being fumigated and with the temperature of the gas and of the com- modity in the tank. It is convenient for commercial fumigations, however, and if proper allowance 1s made for these variations it will be sufficiently accurate for ordinary work. At the end of the fumigation the gas is pumped out of the tank and the vacuum is broken with air. If desired, the fumigated prod- ucts can be “air-washed” several times by alter nately drawing and breaking a vacuum of about 27 inches. In unloading large tanks filled with commodities of an absorbent nature, the residual gas 1s quite noticeable and may affect workmen who remain within the tank too long. It is therefore a wise policy 38 CIRCULAR 369, U. S. DEPT. OF AGRICULTURE to keep the pump in operation during the unloading process so that a stream of fresh air will be drawn constantly through the tank, thus reducing the concentration to which the workmen are exposed. The temperature of the commodity is an extremely important factor in vacuum fumigation. Cold commodities, particularly highly absorbent materials such as flour products, cannot be treated suc- cessfully unless large dosages are used. A temperature of 70° F. or above is desirable. If possible, commodities taken from cold storage should be allowed to come to room temperature before being treated. FiGURH 383.—New type of rectangular fumigation chamber. Note vacuum pump at right, with temperature and vacuum gages and other equipment behind it. FUMIGATION OF VARIOUS COMMODITIES Since it is impossible to discuss here in detail the fumigation of all the many types of commodities that become infested with in- sects, only those commodities most often fumigated in commercial establishments are included in this circular. The fumigation of dried beans and grain in bulk on the farm and in the terminal elevator is discussed in other publications of the Department.* No attempt is made to discuss the fumigation of any commodity from a quarantine standpoint. For more detailed information regarding the treatment of any commodity discussed in the following pages, or regarding commodities not mentioned, the reader should direct inquiries to the Bureau of Entomology and Plant Quarantine, United States Department of Agriculture, Washington, D. C. 4 Farmers’ Bulletin 1260, Stored-Grain Pests; Farmers’ Bulletin 1275, Weevils in Beans and Peas; and Farmers’ Bulletin 1488, Control of Insect Pests in Stored Grain. INDUSTRIAL FUMIGATION AGAINST INSECTS 39 CONFECTIONERY Since the insect problems of the candy and nut-meat industries are rather closely associated, it seems logical to discuss them under one heading. Nut meats are highly susceptible to insect attack, and because they are used in large quantities in the manufacture of candy, they constitute an important source of insect infestation in the candy factory. \\ \\\\\\\ \\ i I Up [TAM] LH Uy My yy Gi y. Y YZ Z Z Z SQV Wines SSS SO ge STURT ASN SE nN AN inp wy i A \ | l oa A | CEE TT ROR ARE EEL Li 22 2 eee 2 ounces each. apne pra i ee eee Ot ey Pe x Sabet ere eae en) 2 OUTICES, The proper quantity of chloropicrin for each floor of the mill should be measured out from the 100-pound cylinders into quart glass bottles or gallon containers and distributed before the fumigation is begun. The measuring should be done outside the building so that the fumes will be dissipated in the open air. The quart bottles should be graduated so that the correct dosage for each piece of ma- chinery can be applied quickly. One pound of chloropicrin equals 91, fluid ounces. The fumigators start at the top of the mill and work down, treat- ing all the machinery and leaving the elevator boots until the. last. Each fumigator must wear a mask equipped with a canister espe- cially adapted to protect against the vapors of chloropicrin. The machinery is treated by sprinkling from the quart bottle di- rectly inside each machine or, if this is impractical, by pouring it in through a hole in one end. Aluminum sprinkler corks can be at- tached to the bottles as they are used. In open mill space the chloropicrin is sprinkled on burlap sacks spread out on the floor, 6-quart sprinkling cans being convenient for this purpose. Care should be taken not to spatter the liquid on the hands or feet, since it might cause blistering of the skin. Where conditions in the mill do not warrant a general fumigation, satisfactory results can sometimes be obtained by fumigating the machinery only. For this type of fumigation the chloropicrin is applied directly into the machines in accordance with the dosage table. The dosage for the reels and purifiers should be increased in proportion to the quantity of stock left in the machinery. In gen- eral, at least 1 pound should be used in each machine. Considerable time is required to ventilate a building that has been fumigated with chloropicrin, as evaporation is slow and the fumigant clings to commodities with great tenacity. When present in flour, chloropicrin has a deleterious effect on its baking quality, but this effect disappears when the flour is aerated. to 6 ounces each. 5A CIRCULAR 369, U. S. DEPT. OF AGRICULTURE LOCAL FUMIGATION A general fumigation once or twice a year does not entirely solve the insect problem in a flour mill, since small infestations are con- tinually developing here and there throughout the milling system. Many millers guard against these infestations by establishing a regular schedule of local fumigations, or treatment of individual machines. Local fumigations can be conducted on. week ends or any night after the mill is shut down. Chloropicrin, hydrocyanic acid, and the ethylene dichloride-carbon tetrachloride mixture are used extensively for this purpose. FUMIGATION WitH CHLOROPICRIN Chloropicrin is used in local fumigations in the same way as de- seribed for general fumigations, except that the individual machines are sealed off from the others. The fumigator should, of course, wear a gas mask. 6 FUMIGATION WITH HTHYLENE DICHLORIDE-CARBON TETRACHLORIDE MIXTURE The ethylene dichloride-carbon tetrachloride mixture is applied by spraying or pouring it into the individual units at the following dosages : Purifier sand tireelss 2 is Ger ee ea aoe 16 to 29 ounces in each conveyor. SIME Ses ee ews ae IS tba teat ee: ee Ly Gunc’: in each section. ROurs CONVEY OTS Ses snare eae 1 to 2 ounces per linear foot. TE ViatOR TPO OCS Hero ee, al ee gee ee 12 ounces. Hlevatorsneads =e a tS sae. le eee 12 ounces to each leg. Other machinery in proportion to size. FUMIGATION WITH HypDROCYANIC ACID Hydrocyanic acid can be applied in several different ways. The same safety precautions-should be taken as in a general fumigation. Workmen handling the material should be equipped with gas masks and all others kept. out of the mill. The machines should be prepared by cleaning out all accumula- tions as outlined in the directions for preparing a mill for a general open-space fumigation. Machines treated separately should be sealed off and made as tight as possible. Calcium cyanide containing 22 to 28 percent of available hydro- eyanic acid is frequently used for this purpose and is easily apphed. A dosage of about 12 ounces for each machine is applied to rolls, purifiers, and sifters. It is spread evenly on dry newspapers in the lower part of the machine. If sifters are equipped with blanks, they should be removed from one section or opening to allow free circulation of the gas. All machines should be m nade as tight as possible, sheets of wrapping paper being placed behind the ventilat- ing doors on the sides of the purifiers. Each elevator leg should be treated with 2 ounces of the calcium cyanide. Calcium cyanide containing 51 to 52 percent of available hydro- cyanic acid is also used for local fumigation work and is applied by means of the special apparatus illustrated in figure 41. ‘This ma- chine draws in caletum cyanide dust through a blower intake, mixes it with air and moisture, and blows the berated hydrocyanic acid INDUSTRIAL FUMIGATION AGAINST INSECTS 55 gas through the outlet hose into the elevator legs, spouts, conveyors, rolls, reels, purifiers, and other milling equipment. The dust 1s retained inside the machine. A dosage of 2 pounds of calcium cy- anide is sufficient for treating four elevator legs and connected spouts and grinders, or for six ordi- nary milling machines. One outlet hose from the machine is inserted in each of two elevator legs, and the blower is operated for about 10 minutes. The hose is then moved to two other elevator legs and the blower operated for 15 minutes. Windows in the mill should be kept open dur- ing the fumigation and for 3 hours there after to allow the fumes to escape. FUMIGATION OF FLOUR WAREHOUSES Warehouses containing flour, feed, or other ce- real products often be- come infested. In the average well-filled ware- house it is impossible. on account of the absorb- ent nature of these com- = Ficurr sa porate HOE DERSNE air through cal “4° : cium cyanide dust in such a way tha 1e hydro- modities, to o bt ain a cyanic acid gas evolved will be free from the dust. complete kill with the dosages generally used. The killing of insects in the open warehouse and in the outer portions of the bageed material is all that can be expected. For this purpose a dosage of 1 pound of lquid hydro- cyanic acid or its equivalent per 1 000 cubic feet of space with an exposure of 24 hours will suffice. VAULT FUMIGATION FOR FLOUR OR CEREAL MILL For the treatment of used bags, returned goods, or small lots of infested flour or cereals, a fumigation vault is almost essential. The vault can be of any of the types discussed on page 28. If possible, it should be located in a building separate from the main mill, so that used bags or returned goods can be fumigated before being taken into the main building. Used bags can be fumigated successfully with any of the fumigants recommended for vault fumigation, and at the same dosages. Bagged flour is fumigated “with difficulty, owing to the excessive absorption of the gas by the outer layers of flour. In vault fumi- 56 CIRCULAR 369; U.S: DEPT. OF AGRICULTURE gations, when the vault is loaded to 25 percent of its capcity or more, the dosage should be based on the weight of the flour to be treated. A dosage of 12 ounces of liquid hydrocyanic acid or its equivalent per ton of flour should be used for an exposure of from 24 to 48 hours 1f the temperature of the flour is 80° F. or above. VACUUM FUMIGATION OF FLOUR PRODUCTS For the vacuum fumigation of flour products at temperatures above 70° F., it is recommended that 2 ounces of liquid hydrocyanic acid per ton be used for an exposure of 3 hours with an absolute pressure of 2 inches or less. The ethylene oxide-carbon dioxide mixture can also be used successfully under the same conditions with the following exposures and dosages: 3 hours, 10 pounds per ton; 6 hours, 4 pounds per ton; 12 hours, 3 pounds per ton. In all cases the gas should be circulated for 15 minutes after it 1s introduced. RICE Rice is grown and stored in the South, where it is subjected to the attack of many of the worst insect. pests of stored cereals. It can, however, be successfully fumigated with a wide variety of materials. For atmospheric fumigation the following dosages of materials can be used per 1,000 cubic feet of space: Liquid hydrocyanic acid or its equivalent, 3 pounds; chloropicrin, 2 pounds; carbon disul- phide, 5 pounds; ethylene dichloride-carbon tetrachloride mixture, 20 pounds; methyl bromide-carbon dioxide mixture, 15 pounds; or ethylene oxide-carbon dioxide mixture, 20 pounds. These dosages are based on an exposure of 24 hours with the temperature of the rice 70° F, or above. Vacuum fumigation is particularly useful in the ‘treatment of rice, and the following dosages are recommended per ton of rice: Ethylene oxide-carbon dioxide mixture, 214 pounds for 1 hour or 114 pounds for 3 hours; methyl bromide-carbon dioxide mixture, 3 pounds for 1 hour or 114 pounds for 3 hours. These dosages should be used with an initial absolute pressure of 2 inches, and the fumigant circulated in the vault for 15 minutes. If the vacuum vault is not equipped for circulating the gas, the dosages should be increased by one-third. Liquid hydrocyanic acid can also be used successfully with a dosage of 5 pounds per 1,000 cubic feet of space with an exposure period of 2 hours. COTTONSEED MEAL Cottonseed meal, stored in 100-pound sacks, if held in certain storages during the summer followi ing erinding, may become se- riously infested with the cigarette beetle (Lastoderma serricorne Fab.). The infestation by this insect in commercially valuable meal is limited chiefly to the outer 2 or 3 inches, whether it is stored in sacks or in bulk. If market conditions indicate that the meal will be carried over the summer, losses resulting from rebates, re- grinding, and resacking can be prevented by fumigation. If insects are already very abundant in meal stored in reasonably tight ware- houses, one thorough fumigation with hy drocyanic acid gas, at the rate of 1 pound of sodium “cyanide or its equivalent per if ,000 cubic INDUSTRIAL FUMIGATION AGAINST INSECTS 57 feet of space, will kill from 95 to 97 percent of the insects. The small percentage escaping this treatment, however, may represent so many in numbers that a second fumigation 3 or 4 weeks later with one-half pound of sodium cyanide per 1,000 cubic feet will be desirable. One fumigation, conducted when the cigarette beetles are first noticed, will usually give a practical control for the summer and fall months provided there is no reinfestation from flying beetles from neighboring meal storages. An early treatment prevents de- struction of the sacks, and the cost of labor and new sacks in repack- ing. The above-mentioned dosages are based on experimental fumi- gations. They are sufficient only for practical control and not for complete eradication. SAFEGUARDS TO BE EMPLOYED IN FUMIGATION WORK In all fumigation work the person in charge should not only ac- quaint himself with the dangers involved, but should bring his assistants together and explain to them the need for caution, and what should be done in case difficulty arises. He should know the first-aid recommendations issued by the manufacturers of the par- ticular fumigant he is about to use. He should employ only men known to be dependable. Members of the fumigating crew should be in good physical condition, with minds alert so that they can act calmly and rapidly and work together according to a prepared and rehearsed plan of procedure. They should abstain from the use of intoxicants. They should take no chances. All persons except fumigators should leave the building.—When an entire building, or any floor, is to be fumigated, all persons in the entire building should be notified in advance and told that they must leave the building between certain specified hours. In large establishments the owners should be held responsible for keeping’ persons out of a building unless they have a definite agreement with the fumigator that he assume all responsibility connected with the safe conduct of the fumigation. It is not always necessary, or desirable, for persons to leave certain buildings while vaults or similar limited areas are under fumiga- tion. Much depends upon the fumigant used, the type of building, and the methods employed for ventilation. The informed fumigator is IN a position to determine what action is necessary. Many routine vault fumigations are conducted daily in congested city areas with- out danger to human life. It is good practice to keep vaults locked during fumigations. If warning signs are left in place permanently, workers may not notice them. : Where a piping system is used to apply a liquid fumigant in a vault, the outside assembly of valves may be enclosed in a wire cage provided with a padlock. Stocks of chemicals used for fumiga- tions should be locked, preferably in a cool place away from main buildings. Danger signs should be posted.—Placards calling attention to the fact that a fumigation is being conducted and warning persons to keep out should be posted on all outside doors of the building. Guards for buildings are desirable-——Guards should be stationed outside buildings, to make certain that they are not heedlessly entered while being fumigated with a dangerous vapor. 58 CIRCULAR 3869, U. S. DEPT. OF AGRICULTURE Gas masks should be available—Gas masks should always be worn during fumigation with hydrocyanic acid gas, chloropicrin, or any other “quickly fatal fumigant. Ethylene oxide, methyl formate, ethylene dichloride, carbon disulphide, and carbon tetrachloride. either alone or in the combinations usually recommended for fumi- gation work, are regarded as only sh ghtly toxic to man as he ordi- narily comes in contact with their vapors in fumigation work, and gas masks are not usually employed unless the fumigators must re- main exposed to their vapors for appreciable periods. Workmen should not be allowed to work in appreciable concen- trations of methyl bromide without wearing masks. Continued exposure to any fumigant useful in insect control will prove fatal to man. Every fumigator should, therefore, obtain in- formation from the manufacturer of the fumigant he intends to use, as well as profit from his own experience, concerning what is a safe attitude to take toward the use of gas masks. Firms selling fumi- gants should be consulted regarding suitable gas masks for protec- tion from their products, or information can be had from the United States Department of Agriculture. Never assume that a gas mask will protect.—Obtain definite as- surance that it is equipped with a canister of chemicals prepared to neutralize the vapor or vapors to be used. Attach a fresh, unused canister to the mask unless the exact history of the one already attached is known. Canisters for gas masks cost only about $2 each. There is no need to take chances. Do not permit familiarity with any dangerous fumigant to lead to criminal carelessness. FIRST AID FOR POISONING FROM HYDROCYANIC ACID GAS Inhaling hydrocyanic acid gas or_absorbing it through the skin is dangerous and must be avoided. If it is absorbed by the system, prompt steps to counteract its action must be taken. Any one or several of the following symptoms may indicate poisoning : (1) Weakness or palpitation of the heart. (2) Headache or dizziness. (3) Rushing of blood to the head (4) Weakness or heavy feeling in the limbs and joints. (5) Nausea and vomiting. (6) Difficulty in breathing, contraction of the chest. (7) Fainting and unconsciousness. If a fumigator feels that he is being affected, he should indicate this to his coworker and together they should leave the building and remove their masks in the fresh air. This makes certain that the affected person reaches the fresh air safely. Men have been known to start for the exit only to become unconscious en route, and if this happens the assistance of the coworker is necessary. If on reaching the outside he is found to be only slightly affected, he can be left alone until he feels fully recovered, w hile the coworker, with another of the fumigating crew, returns to complete the work, If, however, a fumigator has difficulty in walking, becomes un- conscious, or is appreciably affected in other ways, he should be hastily removed from the building to the open air and immediate provision made to keep him warm. INDUSTRIAL FUMIGATION AGAINST INSECTS 59 e Many commercial fumigators think that a man partially overcome by hydrocyanic acid gas should be exercised vigorously. According to Henderson and Haggard," however, a gassed man should under no circumstances be allowed to exercise. “He should neither walk nor even sit up, but must be kept recumbent and as quiet as possible until all symptoms have passed off.” He should not be given hypodermic injections or alcoholic stimu- lants. No liquids should be given by mouth unless the patient is fully conscious. He should not be allowed to return to work until he has fully recovered from the effects of the gas. If the patient has ceased breathing, artificial respiration should be begun immediately, with use of the Shaefer prone-pressure method described below. SHAEFER PRONE-PRESSURE METHOD OF ARTIFICIAL RESPIRATION * 1. Lay the patient on his belly with his face to one side so that. his nose and mouth are free for breathing. Place one of his arms straight out beyond his head and the other under his head, with both hands flat and palms down. 2. Kneel, straddle one of the patient’s thighs, and face his head; rest the palms of your hands on his loins with your thumbs along the index fingers and with fingers spread over lowest or floating ribs. 3. With your arms held straight, swing forward slowly for about 3 seconds so that the weight of your body is gradually, not violently, brought to bear upon the patient. 4, Then, leaving your hands in place, swing backward slowly so as to remove the pressure, thus returning to the position noted in para- graph 2. Then remove the hands to allow the ribs to expand quickly, filling the lungs with air. Swing slowly backward to upright posi- tion, thus relieving the muscles of the back. 5. Repeat deliberately 12 times per minute, swinging forward and backward without interruption until natural breathing is restored or until the doctor arrives. Artificial respiration should be continued 38 to 4 hours if necessary. Loosen all tight clothing about the patient’s neck, chest, or waist and keep him warm by whatever means are available. Next to artificial respiration, the inhalation of a mixture of oxygen and 5-percent carbon dioxide is most useful in resuscitation. By use of a specially designed inhalator the mixture of oxygen and carbon dioxide should be administered for from 20 to 30 minutes immedi- ately after the man is removed from the gas or as soon thereafter as possible. 10 See footnote 3. These directions are summarized from those given by other authors. Complete au- thentiec information concerning this method can be obtained from the U. S. Publie Health Service, Washington, D. C. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED Secsetary.o; AQncuiiiu.e. =... ae HENRY A. WALLACE, Under. Secretary. 222. ee Mi eae Assistant: Secretary Se) te eee HARRY L. BROWN. Director of Extension Work __-2222 2555 = ‘Cc. W. WARBURTON. Director of, Pinance SS =. eee WA. Jer: Derector of information.“ ae eee M. S. EISENHOWER. Director’ of Personnels: 2. =. * 2 Ee W. W. STOCcKBERGER. Hirector: of esearch) |e) 2+ ee ee JAMES T. JARDINE. SOlMG1GOFr 2-S 2 es eee Mastin G. WHITE. Agricultural Adjustment Administration___-. H. R. Totitey. Administrator. Bureau of Agricultural Economics_____------ £ A. G. Brack, Chief. Bureau of Agricultural Engineering_____-__. S. H. McCrory, Chief. Bureau of Animal Industry _______- Sas Baek JOHN R. MouHter, Chief. Bureau of. Biological Survey __- ee Ira N. GABRIELSON, Chief. Bureau of Chemistry and Soils__-___-____--_- Henry G. KnicuHT, Chief. Commodity Exchange Administration ___-___- J. W. T. DuvaL, Chief. Bureau of Dairy Industry Ss O. E. REED, Chief. Bureau of Entomology and Plant Quarantine. LEE A. StTrone, Chief. Office of Experiment Stations_______________. JAMES T. JARDINE, Chief. Farm Security Administration_______--_____-. W. W. ALEXANDER, Administrator. Food and Drug Administration_____-__-____- WALTER G. CAMPBELL, Chief. forest ‘Service 24 ties es wh ee eee FERDINAND A. Sitcox, Chief. Bureau of Home Economices_____ = -__-- ----_ LOUISE STANLEY, Chief. HOP ETY RO BS? Ss a aad UES 3 CLARIBEL R. BARNETT, Librarian. 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