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Combustion Gases of Various Building Materials Organic materials are those which contain carbon. These include many natural products such as wood, wool, cotton, silk, rubber, leather and many synthetic products such as vinyl (polyvinyl chloride or PVC), nylon, rayon, acrylic, TeflonR, StyrofoamR, polyurethane, polyethylene and many more. All organic materials will bum (that is, undergo combustion), although the conditions required for each material to do so may differ. When any material is involved in a fire, it releases smoke, which contains many different combustion products, mainly gases, virtually all of which are toxic. Among these fire gas es, two are always present in a fire, irrespective of the material which is burning because they are the end products of combustion of all organic materials1*2 These are carbon monoxide and carbon dioxide. Wood is a common construction material of natural origin which will, of course, bum. When it does, it can release up to 175 different fire gases. man and of its toxicity in and out of fires. These gases include not only carbon monoxide They all show that CO is toxic due to its fast and carbon dioxide, but also benzene and (200 times faster than oxygen) reaction with acrolein and numerous other irritating, corro hemoglobin in blood to form carboxyhemo- sive and carcinogenic chemicals3'5. globin (COHb)13>14. This leads to lack of oxy gen, resulting in a feeling of drowsiness (nar The nature and concentration of toxic combus cosis) and eventually in death. The hazard of tion products in a real fire will depend on many CO is particularly enhanced by the fact that it is variables and not only on the material which is a colorless and odorless gas which provides no burning. Typically the ventilation to a fire (that warning of its presence. Furthermore, relative is, the size and number of doors and windows) ly low levels of CO are encountered in all is the factor which most strongly controls the smoky atmospheres (a bar, for example) and type of burning (that is, flaming, smoldering or they produce no immediate symptoms of flashover) and thus the toxic gases present in toxicity. the fire atmosphere^.?. Two studies have been earned out in which leading research organiza The amount of CO which is lethal depends on tions equipped fire fighters with devices to ob the age, general health (particularly the pre tain samples of smoke from actual fires for sence of heart disease) and on the level of activ laboratory analysis: the Harvard University ity of the person involved, as well as on other School of Public Health (with the Boston Fire factors such as the presence of alcohol or the Department) in 1979 and the Southwest Re existence of thermal injury. The lethal dose of search Institute (with the San Antonio Fire CO in the atmosphere is estimated to be Department) in 19819. Both studies concluded 138,000 ppm min (that is 4,600 ppm for a 30 that the most hazardous air contaminants in real min exposure)15. A level of COHb in blood fires were carbon monoxide and acrolein. lower than 20% will not lead to death, but any level above this can be lethal12. CO is the most dangerous combustion product present in a fire Carbon Monoxide atmosphere. Carbon monoxide (CO) is present in all fires and, because of its abundance, CO is univer sally recognized as the greatest toxic hazard in real fires10'12. Many studies have been carried out on the effects of CO on Carbon Dioxide CT^oi6752 Carbon- dioxide (CO2) is also present in all fires1. It is generally considered to be non- The Vinyl Institute, A Division of The Society of the Plastics Industry, Inc. Wayne Interchange Plaza II, 155 Route 46 West, Wayne, New Jersey 07470, (201) 890-9299 toxic, but it will, however, increase breathing rates so that it may allow higher concentrations of other, more toxic, gases to be breathed in than would nor mally be the case15. Furthermore, it will displace equal amounts of oxygen. Therefore, CO2 also is dangerous in a fire. Acrolein Acrolein is an extremely irritating gas which results mainly from the combustion of wood, cotton or paper (cellulosics), although some other materials such as polyethylene, polystyrene and oils and fats may also produce it8. Acrolein is frequently pre sent in a fire8*9 and is detectable owing to its odor (odor detection level of 0.2 ppm16). The NIOSH Registry of Toxic Effects17 lists 153 ppm as the dose lethal to man in 10 min (1530 ppm min). The original reference for this entry states "a con centration of 0.35 mg per liter is lethal on 10 minutes' exposure"18. It is difficult, however, to attach any confidence to this statement because there is no associated data or information. Kaplan et al. have studied the effects of 5 min exposures of baboons to acrolein19. No deaths occurred for exposures of less than 1025 ppm. These data show that the lethal dose for acrolein is between 2525 and 5125 ppm min. Acrolein is thus one of the most dangerous gases present in a fire. Hydrogen Chloride Hydrogen chloride (HC1) is an irritating gas which results from the combustion of vinyl and from that of many other flame-retarded materials. It is generally best known as "stomach acid." It dis solves readily in water and it is also eliminated from the atmosphere (air) by virtually all common construction materials (dry-wall, cement, paint, ceiling tile, wood, metal and others)20. It has a sharp, pungent odor (similar to ammonia) which is detectable at very low concentrations (odor detection level 0.8 ppm16). Recent studies by the Federal Aviation Admin istration and by the Southwest Research Institute have shown that baboons are not incapacitated after exposure to levels of ur> to 30,000 ppm of HC1 (3% in air) for 5 min19*21. Additional research conducted by the Vinyl Institute on baboons at the Southwest Research Institute has shown that baboons exposed to 5,000 ppm of HC1 (0.5% in air) for 15 min have received no long-term lung function effects. Furthermore only minimal long term effects on lung function were observed after exposures to 10,000 ppm for 15 min. This means that the lethal dose of HC1 is above 150,000 ppm min, and that exceedingly high levels of HC1 are required to cause incapacitation or death. In the Harvard University study of over 200 real fires in Boston, the maximum level of HC1 found was 280 ppm8, while in the Southwest Research Institute study of real fires in San Antonio, the maximum level of HC1 found was 232 ppm9. This indicates that the concentrations of HC1 found in real fires are much lower than those which could generate fire deaths. Combustion Products of Vinyl Burning vinyl (PVC) produces numerous by products, many of which are exactly the same as those produced by wood or by most other common organic, natural or synthetic materials1*3*5. Carbon dioxide, carbon monoxide and hydrogen chloride account for 97% of the total volume of gases produced by burning vinyl. The remaining 3% consists of benzene and of an assortment of other gases, the composition of which is similar to that of wood smoke22. Neither chlorine nor phosgene are combustion products of vinyl. The National Bureau of Stan dards investigated this problem and found that only traces of phosgene were produced from vinyl wire insulation by any of three methods: thermal decom position in a red-hot furnace, flaming combustion and electrical overload23. However, the appli cation of a 10,000 volt arc to a chamber overloaded with vinyl did generate some phosgene (an average of 26 ppm). This is of no consequence in terms of hazard because, at the same time, such an arc will generate, on its own (even without any wire insu lation), 15,000 to 30,000 ppm of the toxic gas nitrogen dioxide24. This level of toxic gas is 100-200 times more hazardous than the phosgene and will not permit human survival. Thermal decomposition of vinyl can, under certain conditions, generate trace amounts of vinyl chloride monomer (VCM)25, but a flame environ ment will destroy it completely during combustion. VCM can be formed at temperatures above 527F, with maximum levels of 15-30 ppm (compared to 6,000 ppm required to produce dizziness26) at temperatures between 617 and 842F, and is des troyed at higher temperatures. The critical temp erature for human survival in a fire environment is 150F for 1 min27. Conclusions In conclusion, the typical combustion products of vinyl, that is carbon dioxide, carbon monoxide and hydrogen chloride, are either common to all organ ic materials (CO and COo) or of very limited hazard in a fire (HC1). Although there have recently been claims that hydrogen chloride incapacitates people CTL016753 in a fire by "knocking victims down" and making escape impossible, such claims are inaccurate and are totally unsupported by laboratory testing or real fire experience. In fact, the Federal Aviation Ad ministration has recently stated that "ultraconser vative guesses" proposed for incapacitation by HC1 hindered their research by forcing them to expose animals to concentrations 50-100 times lower than those which were eventually found not to be incapa citating28. It is clear, therefore, that vinyl is at least as safe as most other materials in a fire. References 14. DA. Purser and W.D. Woolley, "Biological Studies of Combustion Atmospheres," J. Fire Sci. 1, 118 (1983). 15. B.C. Levin, `Toxicological Interactions of the Primary Gases Found in Fire Atmospheres," A.C.S. Symp. on "Fire and Toxicity. What's New?" Miami, FL, Apr. 29, 1985. 16. J.D. Amoore and E. Hautala, "Odor as an Aid to Chem ical Safety: Odor Thresholds for Industrial Chemicals," J. Appl. Toxicol. 2. 272 (1983). 17. RJ. Lewis and R.L. Tatken (Eds.), "Registry of Toxic Effects of Chemical Substances," N.I.O.S.H., 1979 Edn, Vol. 1.1, p. 61, 1980. 1. C.F. Cullis and M.M. Hirschler, 'The Combustion of Organic Polymers," Oxford University Press, Oxford, 1981. 2. H.L. Kaplan, A.F. Grand and G.E. Hartzell, "Combustion Toxicology," Technomic, Lancaster, PA, 1983. 3. N.W. Hurst and T.A. Jones, "A Review of Products from Heated Coal, Wood and PVC," Fire Mats 2 ,1 (1985). 4. P.J. Fardell, J.M. Baldwin, J.V. Murrell and S.P. Rogers, "Chemical Fingerprints of Fire Atmospheres. Some Results from Full-Scale Fires in a Compartment/Corridor Rig," Fire Research Station BRE Note N 12/81 (1981). 5. P.J. Fardell and Z.W. Rogowski, "Report of the Per formance of the Pittsburgh/Alarie Combustion Model," Fire Research Station, BRE CR21/85 (1985). 6. D. Drysdale, "An Introduction to Fire Dynamics," Wiley, Chichester, 1985. 7. P.H. Thomas, "Fire Modeling and Fire Behavior in Rooms," 18th Symp. (Int.) on Combustion, The Com bustion Institute, Pittsburgh, PA, p. 503, 1981. 8. WA. Burgess, R.D. Treitman and A. Gold, "Air Con taminants in Structural Firefighting." Harvard School of Public Health, NFPCA Grant 7X008, 1979. 9. A.F. Grand, H.L. Kaplan and G.H. Lee, "Investigation of Combustion Atmospheres in Real Fires," Southwest Research Institute, USFA Grant 80027, SwRI Project 016067, 1981. 10. Mi4. Birky, Bid. Halpin, Y.H. Caplan, R.S. Fisher, J.M. McAllister and Aid. Dixon, "Fire Fatality Study," Fire Mats 2, 211 (1979). 11. R.A. Anderson, P.Willetts, K.N. Cheng and WA. Harland, "Fire Deaths in the United Kingdom 1976-82," Fire Mats, 2 67 (1983). 18. A.M. Prentiss, "Chemicals in War" (1st Edn), McGrawHill, New York, 1937. 19. H.L. Kaplan, A.F. Grand, W.G. Switzer, D.S. Mitchell, W.R. Rogers and G.E. Hartzell, "Effects of Combustion Gases on Escape Performance of the Baboon and the Rat," J. Fire Sci. 2, 228 (1985). 20. CA. Bertelo, W.F. Carroll, M.M. Hirschler and G.F. Smith, "Hydrogen Chloride Generation and Decay from the Thermal Decomposition of Poly(Vinyl Chloride) Wire Insulation," 11th Int. Conf. on Fire Safety, San Francisco, CA, 13-17 Jan., 1986. 21. G.E. Hartzell, S.C. Packham, A.F. Grand and W.G. Switzer, "Modeling of Toxicological Effects of Fire Gases: HI Quantification of Post-Exposure Lethality of Rats from Exposure to HC1 Atmospheres," J. Fire Sci. 2. 195 (1985). 22. M.M. O'Mara, "Combustion of PVC," Pure Appl. Chem. 42, 649 (1977). 23. J.E. Brown and M.M. Birky, "Phosgene in the Thermal Decomposition Products of Poly(Vinyl Chloride): Gen eration, Detection and Measurement," J. Anal. Toxicol. 4, 166 (1980). 24. E.M. Carlson, P.G. LeFevre and R.C. Williams, "Insidious Vapors. Infrared Determination of NO2 Generated in a High-Voltage Electric Arc," Anal. Chem. 5$, 1454A (1984). 25. LB. Wakeman and H.R. Johnson, "Vinyl Chloride Form ation from the Thermal Degradation of Poly(Vinyl Chloride)," Poly. Eng. Sci. ], 404 (1978). 26. FA. Patty (Ed.), "Industrial Hygiene and Toxicology," 2nd Edn, Wiley, New York, Vol. H, p. 1304, 1963. 27. A.E. Cote "Highlights of a Field Test of a Retrofit Sprinkler System," Fire J. (May) p. 93, 1983. 12. G.L. Nelson. D.V. Canfield and J.B. Larsen, "Carbon Monoxide - Study of Toxicity in Man," 11th Int. Conf. on Fire Safety, San Francisco, CA 13-17 Jan., 1986.13 * * * 28. C.R. Crane, "Human Tolerance to Toxic Components of Smoke," Proc. Cabin Safety Conf. Workshop, DOT/FAA/ASF 100-85/01, p. 127, 1985. 13. R.D. Stewart. J.E. Peterson, E.D. Baretta, H.C. Dodd and AA. Herrmann, "Experimental Human Exposure to Carbon Monoxide," Arch. Environ. Hlth 24.154 (1970). CTI'0l6754 April 1987