Fire toxicity assessment

In this study detailed fault trees with probability and failure rate calculations were generated for the events (1) Fatality due to Explosion, Fire, Toxic Release or Asphyxiation at the Process Development Unit (PDU) Coal Gasification Process and (2) Loss of Availability of the PDU. The fault trees for the PDU were synthesized by Design Sciences, Inc., and then subjected to multiple reviews by Combustion Engineering. The steps involved in hazard identification and evaluation, fault tree generation, probability assessment, and design alteration are presented in the main body of this report. The fault trees, cut sets, failure rate data and unavailability calculations are included as attachments to this report. Although both safety and reliability trees have been constructed for the PDU, the verification and analysis of these trees were not completed as a result of the curtailment of the demonstration plant project. Certain items not completed for the PDU risk and reliability assessment are listed. 

Purser, D.A. "Toxicity Assessment of Combustion Products and Modeling of Toxic and Thermal Hazards in Fire," SFPE Handbook of Fire Protection Engineering, National Fire Protection Association, Quincy, MA, Section 1, 1988, pp. 200-245. 

Fire safety in a particular scenario is improved by decreasing the corresponding level of fire risk or of fire hazard. Technical studies will, more commonly, address fire hazard assessment. Fire hazard is the result of a combination of several fire properties, including ignitability, flammability, flame spread, amount of heat released, rate of heat release, smoke obscuration and smoke toxicity. 

Toxic potency of smoke data can be used as one of the inputs in fire hazard assessment. In particular, they can be combined with average mass loss rates and times to ignition to obtain a quick estimate of toxic fire hazard. 

T.R. Hull, Challenges in fire testing Reaction to fire tests and assessment of fire toxicity. In Advances in Fire Retardant Materials, D. Price and A.R. Horrocks (eds.) Woodhead Publishing Ltd., Cambridge, U.K., 2008, Chap. 11, pp. 255-290. 

Fire gas toxicity is an essential component of any fire hazard analysis. However, fire toxicity, like flammability, is both scenario and material dependent. Bench-scale assessment of fire gas toxicity either adopts an integrative approach, where the material is burnt in a fixed volume of air, allowing the initially well-ventilated fire condition to become under-ventilated to an unknown degree, or the ventilation is controlled, so that individual fire stages may be replicated. 

NFX 70-100 gives the anomalous result of a higher CO yield for well-ventilated flaming than for under-ventilated. Although hydrocarbons are not always included in a toxicity assessment, their presence is a good indicator of the fire condition. For LDPE, all the tests show a dramatic increase in hydrocarbon yields for under-ventilated combustion. 

The methods for estimation of FED and FEC allow materials developers to assess their products, and if the fire toxicity is likely to be high, to see which species are to blame and take remedial action. Since incapacitation in a fire will result in a fire death in the same way as lethality (unless the incapacitated victim is fortunate enough to be rescued) it is more appropriate to use the incapacitation methodology of ISO 13571 than the rat lethality methodology of ISO 13344. 

T.R. Hull, K. Lebek, A.A. Stec, K.T. Paul, and D. Price, Bench scale assessment of fire toxicity, in Advances in the Flame Retardancy of Polymeric Materials Current Perspectives Presented at FRPM 05, Schartel, B. (Ed.), Herstellung and Verlag, Norderstedt, Germany, 235-248, 2007. 

Consequently, smoke toxicity measurements are often of minimal consequence to fire-hazard assessment. 

Hirschler, M.M., Smoke in fires Obscuration and toxicity, Plenary Fecture, Business Communications Company Conference on Recent Advances in Flame Retardancy of Polymeric Materials, May 15-17, Stamford, CT, Eds. G.S. Kirshenbaum and M. Lewin, pp. 70-82, Norwalk, CT, 1990 Hirschler, M.M., How to measure smoke obscuration in a manner relevant to fire hazard assessment Use of heat release calorimetry test equipment, J. Fire Sci., 9, 183-222 (1991). 

Babrauskas, V., Harris, R.H., Braun, E., Levin, B.C., Paabo, M., and Gann, R.G., The Role of Bench-Scale Data in Assessing Real-Scale Fire Toxicity, NIST Tech. Note 1284, National Institute of Standards and Technology, Gaithersburg, MD, 1991. 

Debanne, S.M., Hirschler, M.M., and Nelson, G.L., The importance of carbon monoxide in the toxicity of fire atmospheres, in Fire Hazard and Fire Risk Assessment, Ed. M.M. Hirschler, ASTM STP 1150, American Society for Testing and Materials, Philadelphia, PA, pp. 9-23, 1992. 

It is important to note that a toxicity assessment based on lethality due to toxic gases is only part of the total fire hazard that needs to be evaluated especially when one is making choices as to the best material for a specific end use. ASTM defines fire hazard as the potential for harm associated with fire. The discussion that follows this definition states, a fire may pose one or more types of hazard to people, animals or property. These hazards are associated with the environment and with a number of fire-test-response characteristics of materials, products or assemblies including but not limited to ease of ignition. 

Robidoux PY et al., Toxicity assessment of contaminated soils from an antitank firing range, Ecotoxicol. Environ. Saf, 58, 300, 2004. 

Purser, P.A. 2002. Toxicity assessment of combustion products, In The SFPE handbook of fire protection engineering. Quincy, Massachusetts NFPA. 

Stec AA, Hull TR. Assessment of the fire toxicity of building insulation materials. Energy Build 2011 43 (2-3) 498-506. 

The first major hazard in process plants is fire, which is usually regarded as having a disaster potential lower than both explosion or toxic release. However, fire is still a major hazard and can, under the worst conditions, approach explosion in its disaster potential. It may, for example, give rise to toxic fumes. Let us start by examining the important factors in assessing fire as a hazard. 

Guide for the assessment of toxic hazards m fire m buildings and transport. Superseded by BS 7899 Parts 1, 2 and 3 but remains cuiTcnt... 

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