This International Standard provides a means for estimating the lethal toxic potency of the fire effluents produced from a material while exposed to the specific combustion conditions of a physical fire model. The lethal toxic potency values are specifically related to the fire model selected, the exposure scenario and the material evaluated. Lethal toxic potency values associated with 30-min exposures of rats are predicted using calculations which employ combustion atmosphere analytical data for carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2) (vitiation) and, if present, hydrogen cyanide (HCN), hydrogen chloride (HCI), hydrogen bromide (HBr), hydrogen fluoride (HF), sulfur dioxide (SO2), nitrogen dioxide (NO2), acrolein and formaldehyde. If the fire effluent toxic potency cannot be attributed to the toxicants analysed, this is an indication that other toxicants or factors must be considered. This International Standard is applicable to the estimation of the lethal toxic potency of fire effluent atmospheres produced from materials, products or assemblies under controlled laboratory conditions and should not be used in isolation to describe or appraise the toxic hazard or risk of materials, products or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire hazard assessment that takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use; see ISO/TS 19706. The intended use of fire safety-engineering calculations is for life-safety prediction for people and is most frequently for time intervals somewhat shorter than 30 min. This extrapolation across species and exposure intervals is outside the scope of this International Standard. This International Standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety and health practices.