دانلود رایگان مقاله تعریف خطر سمی آتش سوزی در ساختمان

Abstract

Fire safe design requires a builder, architect or fire safety engineer to ensure that the available safe escape time (ASET) exceeds the required safe escape time (RSET), for which an estimate of toxic hazard from smoke is required. In Europe, the burning behaviour of construction products must be tested and labelled according to their Euroclass, based on their fire performance in a range of tests. Each Euroclass can be used to indicate a mass loss range. The yields of toxic products may be determined for each material as a function of fire condition. Reliable data has been widely reported from the steady state tube furnace (ISO TS 19700) and the fire propagation apparatus (ISO 12136) for both well-ventilated and under-ventilated flaming. By combining the toxic product yields, most easily expressed as an LC50, with the mass loss range, a methodology is proposed for quantifying the volume of toxic effluent produced by burning construction materials within an enclosure. This allows a maximum safe loading of construction materials to be quantified for a given volume of enclosure. This is intended to ensure that estimates of toxic hazard are undertaken as part of any fire hazard assessment, not to replace more rigorous engineering analyses. It will allow architects and builders to ensure that their materials’ selection does not compromise fire safety.

5. Conclusions

Fires continue to drain society and the economy. Fire safety dominates every aspect of the built environment, from the position of buildings and their internal layout to the infrastructure that links them together. Although fire causes large property losses and relatively few deaths outside the domestic environment, quite rightly, the hazard to life still dominates our approach to fire safety. It is most surprising, therefore, to see the current complete disregard for regulating fire toxicity in the built environment within in Europe and the U.S. The fallacy of the argument that by focusing on ignitability, flame spread and heat release rate, fires can be avoided is demonstrated by the toll of deaths and serious injuries resulting from unwanted fires. The fact that the majority of these result from inhalation of toxic smoke underlines the need for proper regulation. The argument that fire toxicity is difficult to replicate on a bench-scale does not stand up to the weight of peerreviewed publications demonstrating the opposite. This paper describes a simple approach for ensuring that buildings are not filled with sufficient combustible product that a fire can generate a toxic atmosphere, preventing escape and killing the occupants. The approach relies on easily obtained data using the steady state tube furnace (ISO TS 19700), heat of combustion data from either bomb calorimetry (which may be required, as PCS, for Euroclassification), MCC or cone calorimetry, and the data from the SBI test, (necessary to sell construction products for Euroclasses A2 to D within Europe). The method has been presented as simply as possible so that calculation can be undertaken on specific materials, following the methodology described. The results show large differences in the volume of toxic effluents, ranging from a safe loading of 29 m2 of the Euroclass A1 insulation material in a 100 m3 enclosure to 0.2 m2 of Euroclass D Insulation material in the same 100 m3 enclosure, for well-ventilated flaming. For under-ventilated flaming, the differences are similar. 29 m2 of Euroclass A1 material may be safely installed in a 100 m3 enclosure, while only 0.1 m2 of Euroclass D material may be safely installed in the same 100 m3 enclosure. Clearly, 0.1 m2 of 100 mm thick insulation material would not undergo under-ventilated burning in a 100 m3 enclosure, but if the effluent was released from a smaller volume (say 2 m3 ), it would present a toxic hazard in a 100 m3 enclosure. It is important to recognise that the data presented in this paper and the methodology provides a first approximation for estimation of the toxic fire hazard. It is not possible to make more generalised predictions about the actual rate of fire growth in specific scenarios based solely on the performance in the SBI test. There is greater uncertainty associated with the predictions from under-ventilated fires, which burn more slowly but with significantly larger toxic product yields.