Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. L) GAART OrRET ae (at eno Oe ke le > ~ at ei A met SpE ., Van ce U.S. DEPT. OF AGRIC NeTiona mM cr P3197 JUM | PROG L' © - wy S Settee ' Mk ECORL | i MP PRENT WS: WAIHI MD HII | Charles W. Philpot is a Research Forester in the Fire Physics research work unit at Mis- soula, Montana. His B. S. and M. S. degrees in Forestry were obtained in 1961 and 1962, respectively, from the University of California at Berkeley. He received his Ph.D. in Plant Science-Forestry in 1970 from the University of Montana. He was assigned to the Pacific Southwest Forest and Range Experiment Station at Berkeley from 1961 to 1963 and to the Riverside Forest Fire Laboratory in River- side, California, from 1963 to 1966. In 1966 he transferred to Intermountain Station’s Northern Forest Fire Laboratory at Missoula, where he initiated the first fuel chemistry studies. He has shown the chemical composi- tion of plant materials, pyrolytic reactions, and the behavior of the extractives to be im- portant in fire spread, intensity, and fuel ecol- ogy. Gregg M. Johnson is a Physical Science Technician in the Fire Management research work unit at Missoula, Montana. He received a B.S. degree in Chemistry at the University of Montana in 1969. He joined the Northern Forest Fire Laboratory in 1969 where he has The benefits from fire use — including haz- ard reduction, pathogen control, and nutrient recycling — might be forfeited by public reaction to smoke, whether harmful or not. Generally, the public desires alternatives to burning, but might accept fire if direct control of emissions were possible. The effects of diammonium phosphate (DAP) and ammonium sulfate (AS) _ est fire retardant chemicals. the University of Montana. He came to the silvicultural manipulation, times those produced | from the: control. pe AUTHORS ae, ¢ a | 4 been working in fire retardant chemical re- search. Charles W. George was graduated from the University of Montana in 1967 in Forest En- gineering. He received his master’s degree at q the University of Montana in 1969. In 1965, he joined the Northern Forest Fire ators tory staff in Missoula, Montana, where he is now responsible for research dealing with for- Walter H. Wallace, Jr., is a Physical Science Technician in the Fire Physics research work unit at Missoula, Montana. He is currently working on his B.S. degree in Chemistry at Northern Forest Fire Laboratory in 1967 and has worked primarily on fuel chemistry studies. 7 A. David Blakely was graduated from the University of Montana in 1960 in Forestry. He Basan his master’s s degree at the Univers, the Northern Forest mae Laboratory ae Management unit where he is involved in. fire retardant chemical research. “ABSTRACT investigated. ‘Pattionlalet emission ‘rate st oo tal quantity were increased by DAP to several gee ek little ‘increase was | was” ana) pew ie deueat melt a | useful in smoke control through extension of burning periods. 1 4 Bo USDA Forest Service Research Paper INT-117 January 1972 The Effect Of Two Flame Retardants On Particulate And Residue Production C. W. Philpot, C. W. George, A. D. Blakely, G. M. Johnson, and W. H. Wallace, Jr. |.» INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION | « Forest Service U.S. Department of Agriculture “Ogden, Utah 84401 Robert W. Harris, Director CONTENTS CONTENTS FOREWORD)» osc Ste tase acs otersorens Biies SDs A os Oe ee ii PAST RESEARCH ois ssccecgte Rohs A silo hurss, 6-05 oleh See, Oe) Se 1 Effects:of Plame Retardants .: 3.0/3. cde ica dig eee ele ee ee eae aff Retardants’'and’Smoke Production\..2 2328 35 cence = oe seae Oe ie eee 2 Diammonium ‘Phosphate and-Ammonium Sulfate. = ).-0)25..)ce ere ice ree 2 EXPERIMENTAL DESIGN (2% sc. 5 sco is ace wera lee eee 3 The ‘Puel C¥ibs ~ 5, .0..055. 5 sce Se Mi, cS ee PO nooo ae eer etc ee oe 3 Treatment... joecass aac a aia eB ekdts, seh eet Es Hee ee ae Coa ICI ne eo Tas ee ee 3 Burning Procedures iis )s-. 5 scxsisiicse ss: 5) ape Shyam came ee ee 5 Particulate Sampling 22:00. (0:5 [ee Se Rae strc ee eee ee ar ce cea scene ee 5 RESULTS) iss eesesataie ios, arajpay dy aires Mtge ae ee aan he eRe ee eb MEE otect ane eT aT nae ce 7 Treatment. Effect on Thermal Variables#in. Soe a eee ee cece eee 7 Effect on Reside <:s.¢.d0 es ec ae Sperone ae Bho ste a eee ee if Effection Particulate v4.0.0 3.2 shee fe a ee es aE fete os cero cr cia ee Wy DISCUSSION AND' CONCLUSIONS: 5. ohne Sicncyocecepereiees a ciety Cle ene ee cee ine ae 14 The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others which may be suitable. FOREWORD Pressure and criticism currently are mount- ing against open burning of forest debris in the West because of particulate emissions and their visual impact. This controversy has sparked much speculation and some research on alternatives to burning, including better utilization and mechanical treatment of slash. Because fire might be a requirement for fu- ture productivity of the site, it might be im- portant to look at the characteristics of fire itself; specifically, in this study particulate production rates and total amount of par- ticulate. Emissions from slash fires include water vapor, gases, and particulate. The particulate includes both char particles and tar droplets. Several variables are involved in the descrip- tion of particulate emissions: Time and rate of production, total quantity, size distribu- tion, tar composition, and color. Emissions during the smoldering phases of the fire pose a problem in areas of nighttime down-canyon winds and early morning inversions. On the other hand, if atmospheric conditions are stable during the initial stages of the fire, pro- duction rate might become the critical factor. Because the size of the particle determines its settling rate, this variable is important under some conditions. Moreover, the fraction of tar in the particulate becomes important when considering the ramifications of smoke emis- sions, because it might be related to health problems. PAST RESEARGH Effects of Flame Retardants Generally speaking, flame retardants de- crease the maximum rate of combustion and increase the production of char, which is a portion of the airborne particulate from wood fires. Another source of particulate is proba- bly the tar fractions. A retardant that en- hances char and tar production will produce more particulate if it does not in some way also enhance the more complete combustion of the char by glowing. Past work has shown that most flame retardants increase CO, CO, , and H,0 produced from the pyrolysis of wood and cellulosic fuels.' The pyrolysis and combustion of cellulosic fuels can be graphically expressed as involving two competitive pathways. The low energy pathway, which occurs at temperatures around 270° C. or less for cellulose, produces char and relatively large amounts of water and carbon dioxide. The char usually sustains glowing combustion. The high energy path- ' F. Shafizadeh. Pyrolysis and combustion of cellu- losic materials. P. 419-474, in: Advances in Carbo- hydrate Chemistry. R. Stuart Tipson, Ed., Vol. 23. New York and London: Academic Press. 1968. way, which occurs at 340° C. or higher for cellulose, produces flammable volatiles; these support flaming combustion and produce little char or residue. The effect of most pyrolytic flame retar- dants is to emphasize the low energy pathway at the expense of flaming. This is generally characterized by the lowering of the tempera- ture of pyrolysis and an increase in char. The enhancement of the “‘glowing’’ mechanism at the expense of “‘flaming”’ does not mean there will be a decrease in residue following the fire. There may be a relative increase in energy re- leased by way of the low energy pathway, but the total energy released may be decreased be- cause of the residue produced. Whether the residue sustains glowing or not depends upon the chemical composition of the retardant used and the environmental conditions. This is not readily apparent if one considers only pyrolysis. When combustion is included, the picture becomes complicated by the possibil- ity of a retardant catalyzing the glowing com- bustion of the residue as compared to another equally effective retardant that might alter some other combustion phenomenon. Retardants and Smoke Production Laboratory studies have shown that some retardants, such as diammonium phosphate (DAP), apparently polymerize the tars.’ These polymerized tars might lead to the in- crease in smoke. For example, Eickner and Schaffer? found that the most effective fire retardant chemicals, DAP and ZnC2, , greatly increased smoke production in tests on Douglas-fir plywood. Other chemicals tested showed a decrease in smoke density. They al- so found that chemicals previously suspected of promoting postglowing reactions, such as sodium dichromate and ammonium sulfate, also reduced smoke index values. Similar re- sults using particle board were reported by Syska.* Diammonium Phosphate and Ammonium Sulfate The flame retarding effects of DAP and ammonium sulfate (AS) on rate of spread and intensity for wood and fine fuel fires have been tested under controlled conditions.° Findings show DAP to be most effective in slowing spread and reducing intensity. Two other differences between DAP and AS are apparent. The residue remaining after the tests is always much less from the AS treat- ? Thermogravimetric data on file at the Northern Forest Fire Laboratory, Missoula, Montana. 3H. W. Eickner and E. L. Schaffer. Fire-retardant effects of individual chemicals on Douglas-fir ply- wood. Fire Technol. 3: 90-104, illus. 1967. 500 400 300 % @ 200 Percent increase in residue 100 ment. For example, the residue from AS treated excelsior fuel usually is close to non- existent (fig. 1). The other difference is the tremendous amount of black smoke produced by DAP treatment as compared to the much smaller amount of whitish smoke produced by the AS treatment. 4 Arthur D. Syska. Exploratory investigation of fire-retardant treatments for particle board. USDA Forest Serv. Res. Note FPL-0201, 32 p. 1969. ° Charles W. George and Aylmer D. Blakely. Effects of ammonium sulfate and ammonium phosphate on flammability. USDA Forest Serv., Intermountain For- est and Range Exp. Station, Ogden, Utah (in prepara- tion). Sf @ (NH,),HPO, a (NH,),SO, Grams of chemical per square foot Figure 1. — The relationship between residue from spreading excelsior fires and treatment level. EXPERIMENTAL DESIGN The Fuel Cribs This study was conducted under controlled laboratory conditions using a standard fuel crib, which meant we could control the vari- ous environmental and fuel factors and their influence on particulate production and energy-release rate. The cribs were condi- tioned to a known moisture content and chemical treatment was accurately computed. The flow and volume characteristics of the ef- fluent gases were measured and the total con- vection column accurately subsampled iso- kinetically. This type of control is difficult to achieve under field conditions. The cribs were constructed using about 20 pounds (9 kg.) of 3/4- by 3/4-inch (1.9-cm.) ponderosa pine (Pinus ponderosa) sticks, 24-3/4 inches (62.9 cm.) long. These were nailed together with 1-1/4-inch (3.2-cm.) wire brads in a configuration that would insure good combustion and allow insertion of five 24-inch (61-cm.) Douglas-fir (Pseudotsuga menziesii) 4 by 4’s (10.2 cm. by 10.2 cm.). The average dry weight of a crib and 4 by 4’s, Treatment A calibrated spray apparatus was used to apply 10, 20, 30, or 40 percent solutions of each chemical to the cribs and the 4 by 4’s. The preweighed fuel was placed on a dolly and run back and forth under the sprayer un- til completely coated with retardant. The excluding nails, was 44.0 lbs. (20.0 kg.) (tables 1A and 1B). Inasmuch as each crib had a basal area of 4.25 ft. (0.39m? and a load- ing of 10.4 lb. ft.” (50.8 kg. m~ ), they were equivalent to 227 tons acre’ (508,000 kg. hectare”). The approximate heat content of each crib was 8,500 B.t.u. lb.’ (4,722 cal. p:! Noraa4 by: 10” B.t:u.,(9.42 by 107 .cal.). The 4 by 4’s were conditioned in a sealed cabinet maintained at 90° F. (32.2° C.) anda relative humidity of 91 percent. The humidity was held constant by the use of saturated potassium nitrate solutions. Three sample 4 by 4’s from different areas of the conditioning cabinet were weighed daily and sampled for actual moisture content. The cribs were conditioned in a room maintained at 78° F. (25.6° C.) and approxi- mately 30 percent relative humidity; the lat- ter was maintained using a mechanical humid- ifier. The cribs were weighed daily and mois- ture contents were determined from sticks identical to those used to build the cribs. highest treatment levels were achieved by al- ternating several hours of drying with spray- ing. The exact amount of chemical added was calculated after each crib and 4 by 4 reached a constant weight in their respective condi- tioning area (table 1). Table 1. — The weight, moisture content, and chemical treatments of the cribs Crib weights (grams) Stick size 4 in. %4 in. 10,737 9,098 10,509 8,908 9,938 8,585 10,480 8,699 10,092 9,102 10,645 9,069 11,964 8,853 9,996 9,011 10,762 9,101 11,215 9,526 10,268 8,856 10,345 8,861 11,464 9,677 11,629 9,007 10,925 9,112 11,026 8,528 11,303 8,915 11,020 8,692 11,388 8,668 11,238 9,376 10,290 9,093 10,845 9,284 10,005 9,360 10,576 9,270 10,783 9,302 12,224 9,289 11,646 8,823 10,877 10,077 11,037 8,847 11,136 9,129 Total 19,835 19,417 18,523 19,179 Diammonium 19,194 19,723 20,822 19,007 19,953 20,741 19,142 19,206 21,141 20,706 20,037 19,554 Percent chemical Stick size 4 in. % in. Untreated al(S}ac0} 5.8 20.2 6.8 20.2 6.8 Its) 53 5.5 19.4 13.9 15.3 19.3 15.7 16.0 20.0 16.3 16.1 16.0 15.8 17.0 Phosphate Treated 6.8 6.2 5.5 6.3 5.7 5.9 6.6 5.6 6.2 5.9 6.0 5.3 Ammonium Sulfate Treated 21,218 19,712 20,056 20,614 19,179 20,129 19,365 20,026 20,085 21,513 20,469 20,954 19,884 20,265 15.5 13.6 13.7 170 16.9 LES )aC 15.6 16.3 16.9 16.8 15.8 16.8 18.1 16.7 5.3 5.9 6.1 4.7 5.9 5.3 5.8 6.3 5.7 6.0 5.9 6.4 6.6 4.3 Percent moisture Stick size 4 in. ¥% in. * * X * * * * * 0.0 Oi eZ off sll 1.0 5) 1.3 8 PASS) 2.4 3.1 ey 5.6 1.3 5.6 De} 126 ad 8.4 1.5 9.9 2.4 14.8 al H5) ao 1.0 3 ial Ag nD, A 129 A 2.6 th 3.4 1.8 4.9 6 5.6 6 6.8 eT 8.3 Dee, 8.9 Wel 11.3 1.8 ales) Total Te ede St Seay Burning Procedures The cribs were burned on a table placed on a weighing system similar to that described by George and Blakely® (fig. 2). Two methods were used to control temperature buildup around the load cells. A layer of Zonolite in- sulation 3 inches (7.6 cm.) deep was placed between the fuel and the weighing system. This material was found to be thermally stable up to 1,500°C. (2,700°F.); it is not hygroscopic. Streams of compressed air were continuously directed around the load cells during the tests as a further safeguard against temperature changes that could cause elec- tronic drift. The procedure for burning began by condi- tioning the combustion chamber to a temper- ature of 90° F. (32.2° C.) and a relative hu- midity of 20 percent. A slight positive pres- sure was maintained to insure removal of all of the effluent through the stack. The in- duced convection had no measurable effect on the burning characteristics of the fires. The test cribs, including the 4 by 4’s, were placed on the weighing system and ignited at time zero using 100 ml. of a 50:50 mixture of ethanol and acetone contained in two trays. During the following 60 minutes, weight loss and radiant flux from the flame zone were continuously recorded and flame heights were photographed at 1-minute intervals. A Gier and Dunkle directional radiometer with a Particulate Sampling The particulate sampling system consisted of a Neucleonic Corporation of America Model HAS 69 high volume sampler and Gel- men type A glass filter paper. The sampler was connected to a piece of pipe 4 inches (10 cm.) in diameter; this was placed (as shown at top of figure 2) in the center of the effluent stack approximately 50 feet above the fire. The end of the pipe was sealed and four holes Charles W. George and Aylmer D. Blakely. Energy release rates in fire retardant evaluation. Fire Technol. 6: 203-210, illus. 1970. 15°-view angle placed 20 feet (6.1 m.) from the fire was used to measure radiant flux. After the fire went out, the residues from the 4 by 4’s and the cribs were collected and the dry weight calculated. TEMPERATURE FLOW RATE CONDITIONED — AIR INTAKE Meier ae a THERMOPILE cont FALSE CEILING PITOTSTATIC PROBE —~ EFFLUENT STACK ORIFICE PLATE RADIOMETER RECIRCULATION Figure 2. — A schematic representation of the combustion facilities. (Note: not drawn to scale. ) were drilled on the underside. The holes de- creased in size from the center of the stack outward so that the effluent cross section could be sampled equally. The flow rate through the sampler was found to be temperature dependent. There- fore, gas temperature was measured and re- corded at the sampler during a run. Calibra- tion curves were used to obtain actual flow rate. The flow rate up the stack was deter- mined using a United Sensor and Control Cor- poration Model PAE-36-M-W pitostatic probe with an electrical readout. The temperature of the stack gases was measured using a chromel alumel thermopile. Data from the pitostatic probe and the thermopile were used to give stack flow rate as a function of time. This in- formation, along with the sampling rate, al- lowed us to determine what percentage of the total effluent from the fire was being sub- sampled at any given time. Filter papers were dried and preweighed before a test fire. A filter paper was placed in the particulate sampler; upon ignition, the sampler was turned on and flow rate and time were recorded. These readings were recorded at intervals corresponding to a drop in flow rate of 1 ft.2min.-' or 5 minutes, whichever occurred first. A given filter paper was changed when the indicated flow rate was re- duced to 5 ft. ? min.’ (0.142 m.? min."' ). The changes involved a standard 1-minute shut- down time. This procedure was continued for 60 minutes. Contaminated filters were dried and weighed to obtain particulate deposited dur- ing the time the filter was in place. Sample flow rate was corrected to standard condi- tions and then corrected to experimental con- ditions. The average flow rate and the total flow between readings were then computed. The sums of the flows for each filter were di- vided into the particulate accumulated on the filter to give particulate density (mg.m.~°) asa function of time. The densities between filters were interpolated from the adjacent filter data. The rate of particulate emitted and the total particulate produced by the fire were obtained by relating the data from the sam- pler back to stack conditions. The approximate tar content of the partic- ulate was determined by extraction of filter paper subsamples using tetrahydrofuran. The elemental phosphorus content of the particu- late from the DAP treated samples was deter- mined using acid digestion and colorimetry. Water soluble sulfate present in the particu- late was determined turbidimetrically using Sulfaver, a product of Hach Chemical Com- pany, Ames, Iowa.’ The data were statistically analyzed using Program SCRAP (6.0.003) on an IBM 1620 computer. 7Norman A. Huey. Determination of sulfate in atmospheric particulate: turbidimetric barium sulfate method. P. 11-14, in: Selected Methods for the Measurement of Air Pollutants. R. A. Raft, Ed. USDHEW Public Health Serv., Cincinnati, Ohio. 1965. ‘sqyuswzeor1} YZOG Aq psonpad ATTeIyUeYSqns sem APISUBJUT “po}VaIZUN JY} OF AR[IWIS SUOISSIWA peYy SqIIo peyeod} SV OU], “UeWyeeT, Gyq Aq pasearoUl atom A4IY -uenb [e107 pue oze1 UOISSIWa oye[NOTWAeg “pauludoyap sem AjIsua}Ul aI] PUB UOISSIUa oye[NoOYred uO (GY) eyeJ[NS wn -1uoulwe pue (qyq) ajeydsoyd wuniuowwei§p Jo yajja ayy, ‘sot! “A pT “LT T-LNI ‘deg ‘soy “Aleg ysauloyy WAS ‘uoonpoad onptsor pue ayepnorjsed uo syuepsezar VWIR[J OM JO POIJO OUT, “SLET “Ue AOVTIVM “HM pue “NOSNHOF ‘W°D ‘ATANV1E G'V ‘ADUOAD “M‘O “MO ‘LOdTIHd ‘syueWyea1} YZod Aq poonped A]TeryURYSqns sem AjISUd}UT “poyVatZUN 9} OF ILIIUIS SUOISSTULa peYy sqlio poyeol}, Sy oy, “Uewyee gyq Aq poseartoul alam AY -uenb [210] pue 9} UOISSTUd oye[NOIWAeg “paurlWajep sem AjisudzUl oI} pue UOTSSIWA oJe[NOYIed UO (GY) eyeJ[Ns wn -Tuowue pue (qyqd) oeydsoyd wntuowweip Jo yejjo ou], ‘snttt “d PT “LT T-LNI ‘deg ‘soy “Alog ysoI0 J. VS ‘uotonpoad onptser pure oyepnonsed uo syuepseyor awe] OM} JO YaTJO OUT, “SLBT ‘Me “AOVTIVM “HM pure ‘NOSNHOF ‘W "9D ‘ATUMV1E ‘A 'V ‘ADUOUAD 'M'O “MO ‘LOdTIHd ‘syuaWyea1, YYOG Aq paonpead AT[etyURYsqns sem AjISUdJUT “poyeorZUN oY} OF AV[IWIS SUOISSIULa PRY sqiso poyeol] SV a4, “yUeUVaT] Gyq Aq poeseatoul alam AqYy -uenb [e}0} pue o}yed UOISSIUA oFe[NOYIeg “poulwWidajeap sem AjIsua}UL otf pue UOTSSIWa oye[~Noysed uo (GY) azeJ[Ns wn -tuowuwe pure (qyq) eyeydsoyd untuoWUeIp Jo yeajjo aU, ‘snytt “d PT “LT T-LNI ‘deg ‘soy ‘Alas Jsaloyy YAS ‘uotyonpoad anptses pue oyepnoryszed UO syuRpIeyJoI OUIL]Z OM} JO JOOJJo VU, ‘"ZLET “Ue “AOVTIVM ‘HM pue ‘NOSNHOF ‘WD ‘ATAMVIE “GC 'V ‘ADHOUD “M‘'O “MO ‘LOdTIHd ‘syuNUI}eaI} YYOG Aq paonpod AT[eIyUeYsqns sem AjISUd}JUT "pozyeaIZUN JY} OF ABTIWIS SUOISSTWIA pey sqt4o pozeor, SV a4, “WUeUveI] Gyq Aq poasearoUL atom AYTY -uenb [e}0} pue oyeA UOISSIWa oFe[NOYAeG “poaulwdeyap sem AjyisuoqUl aiIlF pue UOISsttWa aye[NoTyAed uO (GY) a7eF[Ns wn -tuowlwe pue (qyq) oyeydsoyd umntuouluetp Jo yoajjo aU, Sot -a7L JlroeNi ‘deg ‘soy ‘Alag YSaIOyT YSN ‘uotonpoad onptser pue ozepnorjsed uo syuepseyor WILT OMY JO JOIJJO OUT, “ZLET ‘Me ‘AOVTTIVM ‘HM pue “NOSNHOF ‘WD ‘ATAMNV1E ‘dC ‘V ‘ADUOUD “M‘O “M'O ‘LOdTIHd RESULTS Treatment Effect on Thermal Variables The effect of the retardants on the burning characteristics of the crib fires is quite appar- ent. Both AS and DAP lowered the maximum weight loss rate, flame height, and radiant energy output. The effect of DAP treatment level on weight loss rate is shown in figure 3 and that for AS level is shown in figure 4. As can be seen, the increase in treatment level lowers the weight loss rate and increases the time to reach maximum intensity. Treatment level refers to the percent of chemical on the cribs, excluding the 4 by 4’s. The graphs of the equations for treatment against maximum Effect on Residue The residue remaining following the fire was related to the type of treatment (fig. 9). The total residue and DAP treatment level had a correlation coefficient R? of 0.87; the R* for AS was 0.21. However, the effects of 2000 1600 1200 Weight loss rate (g./min.) 0 4 8 12 16 20 24 28 32 36 Elapsed time (min.) Figure 3.— Weight loss rates relative to time for several levels of DAP treatment. radiation are shown in figures 5 and 6. The DAP treatments are most effective in both cases. The difference between types of chemi- cals is significant at the 99 percent level as determined by the F test (table 2). The sequential photographs in figure 7 clearly show the effects of the two chemicals on intensity: buildup time is increased and the intensity is decreased (indicated by flame size); DAP was the most effective. Figure 8 shows the three fires at the time of maximum intensity and the residue left following active combustion. the two types of treatment were statistically different at the 99 percent level. The residue from the 4 by 4’s alone was found not to be significant, both within and between types of treatments. 2000 1600 1200 Weight loss rate (g./min.) 0 4 8 12 16 20 24 28 32 36 Elapsed time (min.) Figure 4. — Weight loss rates relative to time for several levels of AS treatment. fa DAP © 7AS A Control Qarz Or Ceenan oananeneses Maximum rate of weight loss (g. /min.) 0 2 4 6 8 10 12 14 16 Treatment level (percent) Figure 5. — The relationship between maximum weight loss rate and treatment level. 1.6 r O DAP | fe) | Ty re) Oo AS | 1.4 Ser? | A Crean, A Control | Maximum radiation (B.t.u./ft.’ — min.) 0 7) 4 6 8 10 12 14 16 Treatment level (percent) Figure 6. — The relationship between maximum radiant flux and treatment level. 66 (LT‘€=a) 00°89 GG z*G60°+XTGV +LL0 L=A €6 pe[ood ayer ayetnonysed 9° 2*G80'—-XL8P'+T 19 S=A ail SV WNUWIXe UI SNsIdA 88° eX8CT'—X8G6 P+8PT 9=A i dvd [Joao] JUSWIYeAL, 66 (LT “€=a4) 00° TSS CS 2XL6'T+X90L'+80'88=A 8% pajood aye[noysed 98" 2X9TZ'— X68'S+88' LV=A ‘Al SV [e107 snsi9aa 86° eXGLL’— XGG'6S+98'SSG=A je dvd [aaa] JUOWIYBAL], ‘SN (quowsaosdunt :ZEe‘Z=4) OP'S 10° XTL0°8-00'ST=A 98 pajood qiso 10° XOTT'-SQ°CT=A 6I SV p Aq H snsi0a 10'> X068'S-CPIT=A ji dvd [oAg] JUOWIYVAL], 66 (ueweaordut :7E°Z=4) SH OF CV’ +GPE'+8S0 3=A 98 pajood anpisel te XGOT'+6LT =A 61 SV Ito snsiaA LS" X9LG'—-G6P'S=A jh dvd [eAg] JUSWIYeALI, 66 (83°€=4) 09°8Z G9 2X€100'+X8€90'- 888° T=A vs pajoog UOT eIpeI 69° -XP0E0' - XP0E0'-ZOP'T=A ST SV WINUITXBU SNsI9A G6" zX*TVO0'+X8P TT -Z8E T=A OT dvd [OAg] JUIWZeAL], G6 (82°8=4) OTP GL’ 2X00Z0'+X8LL9' -09'0T=A ve pejood qystey auery 6L" 2X6800'+XL09P -39' OL=A ST SV UINUITXBU SNSIOA v8" eXT680'+X8P 16 -SG'OL=A 91 dvd JoAg] JUSWIYVAL], 66 (82°8=4) TOOT OL" 2X61'9+X8'6ET - 828° T=A vs pajoog ayed sso] YsTOM OL" 2X68'9+XT SST -OV8 T=A ST SV WINUWTXBU SNSIOA v6'0 2XLG'8+XP' EST -€E8 T=A 9 dvd [aAg] JUSWY ALT], JUuadsad soUBOLTTUBIS A cu uoyenby N - Juewyeary, sdajourereg sdajaupind aif 18a) snoliva JO aduvd1f1Usis 1091)81]0]8 PUD SiskjDuD UOISsaIsaYy — “SG 21QV.L A B C UNTREATED A S—4.55% D A P—4.05% TIME SINCE IGNITION (minutes) 10 20 30 Figure 7. — Sequential photographs showing the burning of: A, An untreated crib; B, a crib treated with 4.55 percent AS; and C, a crib treated with 4.05 percent DAP. TIME SINCE IGNITION (minutes) MAXIMUM FLAME HEIGHT UNTREATED A S—4.55% D A P—4.05% RESIDUE Figure 8. — Photographs of: A, Untreated crib; B, acrib treated with 4.55 percent AS; and C, a crib treated with 4.05 percent DAP, showing maximum flame height and time of occurrence and residue following active combustion. Crib residue (percent) 12 10 Oo ce) oO oO PT TL behets @) gasseese Pe leis oe as sesceneeee oO 0 2 4 6 8 10 12 14 16 Treatment level (percent) Figure 9. — The relationship between crib residue and treatment level. 11 Effect on Particulate The relationship between weight loss rate strikingly different between the two chemi- cals. Figure 10 presents the total accumulated particulate produced from several fires. Ob- viously, the AS treatment had little effect on particulate production, while DAP produced substantial increases in particulate; about 20 times more than that produced by the un- treated at the 14.8 percent treatment level. The rate of particulate is increased and the peak rate occurs further from the point of ig- nition as the amount of DAP increases (fig. 11). The range of particulate produced per unit of weight consumed was 8 to 94 lb.ton"! for DAP: 3:8) to 7.2 lb:tons for AS, and about 5.5 lb.ton"' for the controls, as shown in table 1. The relationship between weight loss rate and particulate production rate is clearly shown in figures 12 and 18. As can be seen, intensity is decreased by both chemicals. Total particulate emitted (grams) OA) ea Se l2 However, there is little change in particulate production by AS. The range in tetrahydrofuran soluble tar was 41 to 56 percent (dry weight of total particulate) for DAP treatment, 15 to 58 per- cent for AS treatment, and 40 percent for controls. The amount of tar was apparently directly correlated with DAP treatment and inversely correlated with AS treatment level. The phosphorus content of the DAP particu- late was 11 to 17 percent, depending on treat- ment level. Preliminary estimates show that about 30 percent of the phosphorus added by treatment is emitted by the fire and can be collected with the particulate. The particulate matter from the AS treated fires was found to contain 33 to 57 percent sulfate, depending on treatment level. How- ever, this did not amount to over 10 percent of the sulfate added by treatment at the high- est level. 14.8% DAP 82.0 615 => 8.4%DAP 2 z-) [0 ae) =! 5.6% DAP cae io) Qa 2 ° o 2.3% DAP 20.5 13% DAP 1.9% AS Control Untreated 0 16, 320) .24 28" 32 36 40 44 48 5275060 Time (min.) Figure 10. — The total particulate produced from fires at several treatment levels. 12 Figure 11. — The production rate of particulate relative to time for various levels of DAP treatment. 300 200 8.4% DAP 5.6% DAP Particulate density (mg./m.°*) 100 12 16 20 24 28 32 36 40 44 48 Time (min.) ame Weight loss rate 80 280 o Dice: eses Particulate Su H Figure 12. — Weight 2 200 5 4 i200 € loss rate and par- 2 resi Base = ticulate production S160 [ : ; 5 _. = rate relative to = 5647 DAP a * = 90 z : E rr = time for three DAP = 120 Phe A 2 [ & 2 | ¢ treatment levels : 7 60 ae ; % and the control. ey ie + 300 40 *e 2g Cone 8 Pie 24 E ro iS = z = mo) = = = 5 a 28 Time (min.) Figure 13.— Weight loss rate and particulate production rate relative to time for three AS treatment levels and the control. 100 m 32 ¢) % 40 44 48 52 56 60 Control ah was Weight loss rate a heat -ses Particulate = 150 680% AS n94% AS a + 12 2 4900 = 3 300 Control 6.80% AS gosetetere, = se. sseesetas eee? x, * ee ps i ee eee oe 8 12 16 20 24 28 32 36 40 Time (min.) DISCUSSION AND GONGLUSIONS Two flame retarding chemicals, DAP and AS, reduced the intensity of large wood crib fires. The DAP treatments were somewhat more effective. However, DAP greatly in- creased particulate production. The AS treat- ments had much less effect on particulate for- mation. Total organic residue was increased by DAP treatment; it amounted to as much as 14 percent original organic weight. As conditions for slash burning are present- ly dictated from a control standpoint, it is being done at low intensities and at times when weather conditions are not conducive to minimum air pollution. This burning results in large amounts of smoke, poor fuel consump- tion, and public displeasure. It might be pos- sible to control intensity during the drier months, keep smoke production down, and insure more complete combustion by chemi- cally treating the slash. Obviously, DAP would not do the job. This study supports the possibility that 14 DAP does polymerize the tars and make them more thermally stable. If these tars become less available to combustion, they will add to the particulate in the effluent. Apparently, a large amount of the phosphate ends up as some form of phosphorus in the particulate. The question of why AS and DAP act differ- ently in particulate formation might parti- ally be answered by continued study of the effects of phosphate on the tars. Future research starting with determina- tion of the difference in retarding mechanisms (and therefore in particulate and residue pro duction) between AS and DAP could lead to the development of chemicals that catalyze glowing to the point of practically no flaming or effluent. The importance of fire in the forest is be- coming more evident every day. Perhaps fu- ture research and land management personnel should be directed more toward fire controls rather than to “‘alternatives to fire.” yt U.S. GOVERNMENT PRINTING OFFICE: 1972 - 780 -623/80 REGION NO. Headquarters for the Intermountain Forest and Range Experiment Station are in Ogden, Utah. Field Research Work Units are maintained in: Boise, Idaho Bozeman, Montana (in cooperation with Mon- tana State University) Logan, Utah (in cooperation with Utah State University) Missoula, Montana (in cooperation with Uni- versity of Montana) Moscow, Idaho (in cooperation with the Uni- versity of Idaho) Provo, Utah (in cooperation with Brigham Young University )