This test method has been designed to provide data for the mathematical modeling of fire hazard as a means for the evaluation of materials and products and to assist in their research and development.
This test method is used to predict, and subsequently confirm, the lethal toxic potency of smoke produced upon the exposure of a material or product to specific fire test conditions. Confirmation determines whether certain major gaseous toxicants account for the observed toxic effects and lethal toxic potency. If a predicted lethal toxic potency value is not confirmed adequately, indicating a potential for unusual or unexplained toxicity, the lethal toxic potency will need to be investigated using other methodology, such as conducting an experimental determination of the LC50 using the apparatus described. (See X1.3.1 and X1.3.2.)
This test method produces lethal toxic potency values that are appropriate for use in the modeling of both pre-flashover and post-flashover fires. Most fire deaths due to smoke inhalation in the U.S. occur in areas other than the room of fire origin and are caused by fires that have proceeded beyond the room of fire origin. It is assumed that these are flashover fires. Therefore, the principal emphasis is placed on evaluating toxic hazard under these conditions. In post-flashover fires, large concentrations of carbon monoxide results from reduced air supply to the fire plume and other room-scale factors. Bench-scale tests do not have the capacity to simulate these phenomena. The lethal toxic potency values determined in this test method are obtained from fuel/air ratios more representative of pre-flashover, rather than post-flashover conditions. In cases where a pre-flashover fire representation is desired in fire hazard modeling, these LC50 values are appropriate. Lethal toxic potency and carbon monoxide yield values determined in this test method require adjustment for use in modeling of the hazard from post-flashover conditions. (See X1.4.1.)
The lethal toxic potency values determined in this test method have a level of uncertainty in their accuracy when used to predict real-scale toxic potencies. (See X1.4.2.)
The accuracy of the bench-scale data for pre-flashover fires has not been established experimentally. The combustion conditions in the apparatus are quite similar to real pre-flashover fires, although the mass burning rate may be higher at the 50 kW/m2 irradiance of the test method.
Comparison of the toxicant yields and LC50 (post-flashover) values obtained using this method have been shown in limited tests (22) to reproduce the LC50 values from real-scale, post-flashover fires to within an accuracy of approximately a factor of three. Therefore, LC50 (post-flashover) values differing by less than a factor of three are indistinguishable from each other. (See X1.4.2.)
This test method does not attempt to address the toxicological significance of changes in particulate and aerosol size, smoke transport, distribution, or deposition or changes in the concentration of any smoke constituent as a function of time as may occur in a real fire.
The propensity for smoke from any material to have the same effects on humans in fire situations can be inferred only to the extent that the rat is correlated with humans as a biological system. (See X1.2.5.)
This test method does not assess incapacitation. Incapacitation must be inferred from lethal toxic potency values.
The effects of sensory irritation are not addressed by this test method.
1.1 This fire-test-response standard covers a means for determining the lethal toxic potency of smoke produced from a material or product ignited while exposed to a radiant heat flux of 50 kW/m2 for 15 min.
1.2 This test method is limited to test specimens no ......
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