Fire research abstracts and reviews: Volume 13, 1971 (1971)

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THE ROLE OF CHEMISTRY IN FIRE PROBLEMS— A CHEMIST'S SUMMARY R . F R I S T R O M Applied Physics Laboratory, The Johns Hopkins Umverstty This symposium has presented a senes of papers outlining the contributions which chemistry has made and contmues to make in the areas of: Combustion, Thermodynamics, Chemical Kmetics, Analytical Chemistry, Polymer Chemistry, and the Chemistry of Fire Retardance and Suppression. Both the potentiahties and the limitations of chemical information have been discussed. Chemistry is, of course, only one of several sciences which play important roles m fire problems and the mteractions between these are strong. Nevertheless, i t is a usefiil exercise to consider the contributions of chemistry as an entity although it should be kept m mmd that i t is the marriage of information from these various disciphnes which leads to the complete understandmg of the fire problem which we seek. This paper will provide a summary of the contnbutions of chemistry; not from the standpoint of the mdividual chemical disciphnes, an approach which has already been well done by our speakers, but from the standpomt of the various problem areas. This gives a different and hopefully productive perspective on the problems of fires and the role which chemistry can play. To a degree, the classification of fire problems is a matter of taste; for discussion we will arbitrarily divide fire problems mto five categones correspondmg to the time sequence durmg a fire. I . FIRE HAZARD PROBLEMS—What should be done before the fire. I I . FIRE DETECTION PROBLEMS—How to discover the problem be- fore i t gets out of hand. I l l FIRE PROPAGATION—How rapidly will a fire progress. IV. FIRE SUPPRESSION PROBLEMS—What can be done to curb a fire. V. FIRE SALVAGE PROBLEMS—What can be done to reduce the loss. Each of these problems has two aspects: A. Evaluation of the problem. B. The countermeasures to the problem. 273

274 FIRE HESEARCH Fure Hazard Problems The evaluation of fire hazard reqmres an understandmg of chemistry. This mvolves both a quahtative and quantitative problem (1) can a material be oxi- dized, (2) if igmted, what heat is released and what compounds are produced, (3) how easily is i t igmted and how rapidly will i t progress. In the fuel-oxidizer loadmg problem, thermodynamics furnishes a powerful tool which Dr Stull has discussed m some detail Fuel loadmg is commonly con- sidered the major problem but i t is a two-fold problem; fuel and air availability. The usual assumption is that the oxidizer is the air and that i t has unlimited avadability. This is not always the case and often this can be of practical use or be a senous problem. For example, m a 15'X 20'X10' room there is only oxygen and only a third of this is available before a fire extmgmshes itself for lack of oxygen. This IS not a large amount so that if i t were possible to isolate such a room, a fire would consume only a few pounds of fuel. Thus, one approach to fire suppression can be isolation. There are two problems with this approach, one is the life hazard m such an environment and the other is the flare-up hazard to firemen entermg such a compartment and allowmg air to suddenly contact hot, combustible gases An added problem is the mcreased use of oxidizmg substances—ammonium nitrate fertihzers—perchlorates for swimmmg pools, two potent sources of oxygen Despite these complications, i t is well within the capabilities of modem chemistry, usmg modem computmg techmques, to furnish a meaningful answer to this problem. I f the problem is orgamzed and questions posed correctly, meamngful answers can be provided economically. The second problem m hazard evaluation is igmtabihty, and here i t is possible to divide materials mto classes chemically but effects of geometry and position must also be considered. Ignition has been treated as an empincal problem, but i t IS high time that this empiricism is rationahzed by the mtroduction of basic chemistry and the physical heat transfer. I feel that this is both feasible and neces- sary I t often mvolves both gas phase chemistry and sohd phase chemistry which you have heard discussed by Drs Berl, Fnedman and Wall. The third question is propagation probabihty. This is a complex problem which IS not completely divorced from igmtabihty. Here agam chemistry has basic mputs m the form of chemical kmetic constants and reaction mechamsms Again a strong effort to connect the empiricism of the tests with the basic chemical and physical information is long overdue. Much of the basic information is already avadable and much of the information which is presently not available would be forthcoming if i t were clear that the information would be used. The basic research worker can fumish relevant mformation if an outhne of the areas of need is made. Agam, this requires a viable theory connectmg the empirical descriptions with the elementary processes. The foiuih area is life hazard toxicology. Here chemistry can furnish information on possible products and conditions for their formation which m turn must be evaluated toxicologically. A wealth of information is available, but the area has not been systematized. Agam the relation between practice and available basic information is the weak hnk. Followmg this evaluation, methods for reducmg the hazard should be explored. The use of fire retardants is an important area. This is a predommantly chemical

ABSTRACTS AND REVIEWS 275 problem mvolvmg complex sohd and heterogeneous phase chemistry. Here much information is available, but i t requires more systematic evaluation. Both Dr. Wall and Professor Emhom discussed these problems Trade-offs between flam- mabihty and toxic combustion products may be necessary. This, I feel, is a par- ticularly fruitful area for a chemist to make contnbutions to the fire problem Automatic suppression systems can be improved by an imderstandmg of chemistry. Both the combustion chemistry itself and the chemistry connected with flame extmguishment offer a wide area for chemical contributions. Code recommendations are a powerful tool m reducmg fire hazards and an understandmg of the chemistry mvolved in hazard evaluation should be an im- portant contribution Fire Detection Systems Fire detection can m prmciple be based on chemical information. My own feelmg is that i t is urgent that fire detection be mvestigated relative to the question of saving life Most fire detectors were designed for property safeguardmg and heat sensors are commonly used Life protection makes the chemical methods of detectmg and wammg methods of particular importance, smce the smoke and toxic gases are the major life hazard in a fire With the exception of smoke de- tectors, chemical detectors have not been widely used I t is possible that chemical detectors for CO, Hydrocarbons, CO2, HCN etc. may be practical and offer an important addition to the detection systems—perhaps not as a complete substitute for heat and smoke detectors, but as alternate detectors to mcrease sensitivity and reduce false alarms Fire Suppression Problems The chemistry of fire propagation and inhibition plays a key role m the choice and understandmg of suppression systems Much progress has been made in understandmg gas phase chemistry, and you have heard the wealth of work on pjTolysis of solids and heterogenous oxidation processes. Much work still remains to be done, but information is available. What is needed is to organize the m- formation, and understand the problem to the degree where we can systematically ask the chemist the key questions. This reqmres models of a sophistication not yet available, but this is a goal worth stnvmg for Some attempts have been made and this is an area where basic chemistry can offer vital information on mechamsms When these roles are understood, basic rate and thermodynamic mformation can be utihzed. I f we knew the correct questions, i t is probably well within the present capabiUties of chemical researchers to furmsh the required information on a reason- able time scale for practical use. Fire Salvage This is an area where research has made httle contribution but i t would appear to be a frmtful area to mvestigate. Chemistry could suggest where damage is potentially reversible and give a value judgment on the economics of such measures

276 FIRE RESEARCH An understandmg of this field involves almost the whole of mdustnal chemistry. In this context one should consider both people and property. I t would be desirable to develop an understandmg of the health hazard which exposiure fixe entails so that recommendations can be made to physicians and administrators on likely post fire problems. This understandmg is coupled with the evaluation of the ongmal hazards coupled with a knowledge of what actually was burned. Summary Fire problems are vaned and many of them involve chemistry m some form. The efficient use of chemical information will only come about by a marriage of the empincism which has dommated the fire field with an mtelhgent use of basic information, A wealth of information is avadable, but i t is not clear which pieces of information are required, which pieces are available and what basic information is still required. What is necessary is a dialogue between the practitioner and the research worker so that the critical pieces of information can be located, described and developed systematically. The contnbutions of chemistry to the overall problems of fire can and should be important, but a sympathetic understanding and exchange of information is required between the practitioner and the basic researcher.