Gases from Thermal Decomposition of Common Combustible Materials JOHN C. OLSEN,GEORGEE. FERGUSON, AND LEOPOLD SCHEFLAN The Polytechnic Institute of Brooklyn, Brooklyn, N. Y. N A previous article (4) the
c a p a c i t y of 0.98 cubic m e t e r The gases f r o m all types of $res investigated (34.61 cu. ft.) was used for the results of a s t u d y of the contain toxic constituents in suficient amount combustion experiments (Figure gases p r o d u c e d by the to make breathing the gases dangerous or even 1). This b o x was e q u i p p e d decomposition of nitrocellulose fatal in a relatively short period. Gases f r o m with a glass door which could be and cellulose a c e t a t e photodifferent materials difler greatly in toxicity. tightly sealed. Openings were graphic films were reported. p r o v i d e d for w i t h d r a w i n g The investigation was c a r r i e d Substances containing nitrogen or sulfur, or both, samples of the gases produced out to determine the cause of produce the most toxic gases. for analysis. the loss of l i f e of a b o u t 125 Of the textiles used for clothing, draperies, etc., A small building c o n s i s t i n g persons resulting from the Clevecotton and rayon produce the least toxic gases, of a single room of 31.27 cubic land Hospital fire, In addition whereas silk and especially woolen materials meters (1104 cu. ft.) capacity, to such c o m m o n l y occurring lined with asbestos and having gases as carbon monoxide, cargive off such deadly gases as hydrogen sulfide, three windows and a door, was bon dioxide, and pyroligneous hydrocyanic acid, sulfur dioxide, ammonia, and also available for fires on a larger acid, such h i g h l y t o x i c gases carbon monoxide. scale. This room was fitted with as nitrous fumes' and prussic While the breathing of air containing more openings for sampling the gases acid were f o u n d . The great from the 0,305-, 0.610-, 0.914-, than 2 or 3 per cent of carbon dioxide causes loss of life in this fire was due to 1.22-, 1.52-meter (1-, 2-, 3-, 4-, the i n h a l a t i o n of these toxic a n increase in the involuntary frequency of and &foot) levels from the floor gases and not to direct injury by breathing which m a y become very distressing, (Figure 2). This arrangement the fire itself. As the nitrous the gases f r o m most combustible materials also made it possible to study the disfumes were p r e s e n t in great contain more or less acrid or ill-smelling contribution of gases w h i c h may volume, this gas was undoubtstituents. The physiological effecl of attempting occur in rooms. Although the edly the most important factor room was equipped with fans, in the loss of life. A l t h o u g h to breathe such gases results in a n involuntary ordinarily no attempt was made the prussic acid was found only reduction of respiration and forces those breathto mix the gases before sampling. in small amounts, it is so deadly ing the f u m e s to seek fresh air. These effects It was found that g e n e r a l l y that it could not be considered have undoubtedly been the means of sacing lives. three distinct layers of gases a negligible factor. Other fires were present-namely, one a t the have occurred in which there has been great loss of life even though only ordinary com- ceiling, one on the floor, and a n intermediate iayer which bustible substances were burning. A case of this kind is the consisted of more nearly pure air than either of the other two. fire in the Columbus penitentiary, in which 320 lives were lost. The relative purity of the intermediate layer was very noticeHere many of the prisoners were locked in their cells and were able to the operatives breathing the air. The hot products overcome by the gases from the fire even though the heat and of combustion were found a t the ceiling, and the heavy gases resulting from distillation were found on the floor. At times flames did not reach them. The total number reported to have lost their lives from fires these layers of gases could be seen as distinct strata. The in the United States reaches the appalling figure of 10,000 lighter gases from each layer tended to diffuse throughout the annually. Since many of the victims of the Cleveland room more rapidly than the heavier constituents. When the disasters were not burned but only gassed, it is reasonable to fires were allowed to continue burning, the composition of assume that a large percentage of those reporteg, in the past, the gases in the room became more uniform. as burned to death in conflagrations have, in reality, sucThe combustible materials used for experiment included cumbed to gases and not to flames. wood or cellulose materials, oils such as gasoline, textiles such as wool and natural silk, and articles containing rubber DECOMPOSITION PROCEDURE such as electrical insulation. Selection of these was made In this investigation the same general methods were em- on the basis of their chemical composition as well as their ployed as in the one previously mentioned (4). The ma- physical properties, both of which affect the character of the terials studied were decomposed by heating in the absence combustion products. Materials composed of cellulose (such of air or oxygen and also burned in the presence of excess of as wood) contain mainly carbon, hydrogen, and oxygen; air. I n most commonly occurring fires, both conditions gen- they burn with a flame produced by the volatile combustible erally prevail. Part of the material burns while other por- gases given off during the fire and also form incandescent tions are decomposed by the heat without much oxidation. carbon. Such materials give a gaseous product containing Thermal decomposition was carried out in flasks, described a much higher carbon dioxide content and a much lower in the preceding article. A sheet iron box having a cubic oxygen content than materials such as oils and gasoline, which burn only by a flame which is extinguished when the oxygen 1 The term "nitrous fumes" has been commonly used t o designate the content drops to about 16 per cent. The gas produced may brown mixture of NZOS and NzOd which results from contact, of KO with the contain a considerable percentage of volatile hydrocarbons oxygen of the air at ordinary temperatures. N10 is only slightly toxic.
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and aim a high percentage of finely divided carbon if the material is permitted t o burn out. Among the commonly used textiles, cotton is composed of cellulose and rnll glve products simllar t o wood. Rayon will give the same deconiposition products as cotton. Natural silk contains, in addition to carbon, hydrogen, and oxygen, a large percentage of nitrogen. The composition of silk fiber (6) is: carbon, 48 3 per cent; hydrogrn, 6 5 ; oxygen, 26.0,
Vol. 25, No. 6
monmde; bulb 7. a slow-burnw pipet of the Hddane type filled with water for the determination ci methane sad hydrogen; bulb 8, filled with Rater and used to store samples of gas during Ammonia was determined by absorbing a memured volume of the gas in a known volume of standard a d The excess of acid
2:
~ ~ ~ ~ ~ tlon. Total Rmmonis in this ilquld was determined by dLstillation (after makmg alkalmne) and titration of the distillate
Hydrogen cyamde wa8 determined by the mothod given m the previous article (4) The amount of hydrogen sulfide w86 determined by absorbm g it from a measured volume of the gas Ln an ammomacd solution of cadmium rhlonde, cont a i n i n g 30 g r a m cadmium chloride, 1100 cc water, and 1200 cc ammonium hydroxide The precipitated cadmium sulfide w m determined by dissolving in an exceSs of roncentrated hydrochloiro and and txtratmg with standard iodine iolution Sulfur dioxide v a s determined by passing a known volume of the gm through bromine water, boding out the cxeess bromine. precipitatm,q and weighing barium sulfate. Both hydrogen aulfide and sulfur dioxide were seldom present m the iame gas DECoMPoSlTION A h D COXHUbEION OF
FIGURE 1.
SHEbT
IRONBox FOR COMBUsTION EXPERIMENT* WTTH ARWHPTION TRAINS
and nitrogen, 19.2. Various nitrogen compounds, as well as free nitrogen, might be formed by the docomposition of this material. Wool, in addition to the constituents present in silk, contains sulfur, the composition (6) being: carbon, 50 per cent: hydrogen, 7.0; oxygen, 22 to 26; nitrogen, 15 t o 17; and sulfur, 2 t o 4. This percentage of sulfur is high as a potential source of dangerous gases. The decomposition of wool, as well as all materials consisting of the hair of animals, might he expected to evolve a variety of simple nitrogenous as well as sulfur compounds, inany of which not only have a disagreeable odor, but are also highly toxic. Wool and all animal fibers are quite fire resistant. Unless cotton, rayon, or. unweighted silk fabrics are present in considerable quantity, woolen garments do not burn a t all readily. As is usual with fires, distillation products as well as tho products of more or less couiplete comhustion are found in the gases evolved. The essential constituent of unvuloaniaed rubber is polyprene (CRH,,) which burns with a smoky flame giving off volatile hydrocarbons, carbon monoxide, and carbon dioxide. Compounded rubber, such as is used in insulation, contains sulfur and various filling materials. The disagreeable odor given off by such rubber when burning is due to various sulfur compounds; the gases evolved might contain a number of highly toxic sulfur gases and the disagreeable odor would have a suffocating effect. A special eight-bulb Orsat apparatus was deaigned and eonstrueted for the analysis of the complicated gas mixtures. The gweous constituents were determined in the order named by the following rementu: bnlb 1, one purt of caustic potnsh to two parts of water for the nbsorption of acid gases such as carbon dioxide, hydrogen sulfide. hydroKen cyanide, and pyroligneous acid; bulb 2, 3 N sulfuric acid for the :,bsorption oi basic g&?es such as ammonia and volatile organic bases; hulb 3, saturated bromine water for tho s!,sorption of unssturated hydrocarbons; bulb 4,B high-bailing paraffin oil for the absorption of saturatcd hydrocarbons; bulb 5, yellow phosphorus and water for the absorption of oxygen; bulb 6, a hydrochloric acid solution of cuprous chloride with copper wire for the absorption of carbon
CEI~LUI.OSE A partial study had already been made of the gases produced from cellulose in the previoub article (4). Table I shows that highly toxic concentrations of carbon dioxide and monoxide are produced when cellulose is decomnosed bv heatine in the absence of air. The
. Carbon diurido Carbon monoxide Ilydrogcn Acid (acetic) Methsne Unsatd. hydrooarbone Tol,eI gases:
co.per WBm
Cubio feet per pound
. A
B
C
11
%
%
%
%
%
49.4 36.5 4.4 1.6 8.1 0.0
43.2 41.5 0.0 1.6 11.5 2.2
44.7 57.1 10.1 1.6 4.9
47.2 37.1
1.6
46.1 38.1 5.4 1.6 7.5 1.4
55 0.88
58
56 0.90
59 0.94
57 0.91
B",
