Downloaded from https://www.everyspec.com MIL-STD-2031(SH) APPENDIX F N-GAS MODEL SMOKIi TOXICITY SCRKIZNING TE.ST 10. SCO1’E 10.1 Scope. This laboratory test method shall dctcrminc whether the combustion products from a material are extremely or unusually toxic. It shall be hased on a method prepared by the National Institute of Standards and Technology (NIST) from their experiments conducted with rats on the combined lethal concentration of the major fire gases. The test shall be for preliminary screening purposes to rapidly estimate toxicity and shall provide information on the gases responsible for toxicity.
The test method shall assume that the toxicity of combustion products is determined by a small number of major fire gases. The procedure shall entail burning samples of test materials in one of three modes: flaming, non-flaming, and non-flaming/flaming transition. Analytical tests are first conducted without animals. The concentrations of a small set of gases are measured - CO, C02, HCN, and low 02 Based on the N-Gas Model equations for this combination of gases, an LC50 value is predicted for the material. Ve~ low predicted LC50 values indicate that a material has extreme toxicity. Tests arc then conducted w“th laborato~ rats at 80 percent of the estimated LC$OO value.
If none of the animals die from a 30 minute exposure or within a 24 hour post-exposu}e period to these gases, the predicted LC50 is considered usable for hazard assessment calculations and indicates that the combustion products do not contain an unusually toxic material. If any animals die, then other gases are present that interact with the initial set of four gases to affeet the toxicity of the combustion products. This ~ult mea?w that further toxicity testing shall be neeessary m identify my unknown toxiesnt and to cktermine a more precise LC50 value for the material.
The advantages of this screening test over current test methods that ~ smoke tumicity we that it is rapid, economkxd, minimizes the use of animab as acwnpared to “classical LC50” determinations, and provides information on the gases responsibk for toxicity in addition to the potency of the combustion gases. This appendix is a mandatory part of the standard. The information contained herein is intended for compliance. 20. APPLKABLE DOCUMENTS 20.1 Government documents. 20.1.1 Other Government documents, drawings, and publications. The fohwitxg other documents, drawings, and publications form a part of this document to the extent specified herein.
Unless otherwise speeitied, the issues are those cited in the the solicitation. NATIONAL INSTITUTE OF HEALTH (NIH) Guide for the Care and Use of Laboratory Animals (Application for copies should be addressed to the Superintendent of Documents, U.S. Government Printing Oftice, Washington, DC 20402.) 31