Significance and Use
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.
Scope
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 larger than 76 by 127 mm (3 by 5 in.), with a thickness no greater than 51 mm (2 in.). Specimens are intended to be representative of finished materials or products, including composite and combination systems.
1.3 Lethal toxic potency values associated with 30-min exposures are predicted using calculations that use combustion atmosphere analytical data for carbon monoxide, carbon dioxide, oxygen (vitiation) and, if present, hydrogen cyanide, hydrogen chloride, and hydrogen bromide. The predictive equations are therefore limited to those materials and products whose smoke toxicity can be attributed to these toxicants. An animal check determines the extent to which additional toxicants contribute to the lethal toxic potency of the smoke.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard measures and describes the response of materials, products, or assemblies in response to heat under controlled conditions, but does not by itself incorporate all factors required for fire hazard of fire risk assessment of the materials, products, or assemblies under actual fire conditions.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations (particularly with regard to the care and use of experimental animals) prior to use. For specific hazards statements, see Section 7 and Note X1.1.
