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Under the Montreal Protocol, an international treaty, the production of the fire and explosion protection agent Halon 1301 (bromotrifluoromethane, BFC-13B1, CBrF(3)) was phased out in the United States at the end of 1993. No environmentally acceptable halon substitute that is equivalent to the existing halons in toxicity effectiveness, and dimensionality has been identified. The objective of the overall effort is to assess compounds containing members of the main group elements as fire extinguishants and has potential halon replacements.

Current commercially available Halon 1301 replacement compounds (other than CF3I) lack the fire suppression effectiveness of halon primarily because they do not contain bromine in their molecular structure. Bromine is thought to catalyze radical recombination reactions which deprive the combustion process of the (dot)OH and (dot)H radical species which promote the combustion of fuel molecules in the gas phase. This project was conceived to develop new fire suppressants incorporating bromine by basing the compounds on chemical families with expected or demonstrated short atmospheric lifetimes. These compounds are said to be tropodegradable bromocarbons. The targeted chemical families in order of importance were partially fluorinated alkenes, ethers, and amines. The alkenes have now been shown to have very short lifetimes on the order of days. This project identified several low boiling brominated and partially fluorinated alkenes, ethers, and amines with potential of meeting the toxicity, fire suppression, and environmental criteria currently identified under the EPA's SNAP program for halon replacements. Several of these tropodegradable compounds were subsequently acquired and their cup-burner flame suppression performance evaluated with promising results. Several of the bromofluoro alkenes have now also been evaluated in an acute inhalation toxicity test which yielded extremely promising results for this chemical family. This is an interim report covering the first phase of an ongoing effort.

Although it is not certain that a drop-in" chemical substitute (as opposed to a new technology) for halons that can be used in normally occupied areas will ever be identified, there are two promising paths to such an agent. The first is to target bromocarbons with very short atmospheric lifetimes. We refer to these materials as Tropodegradable Halocarbons." The second path is to develop non- halocarbons- chemical 5 that are unlike the classic halocarbon agents used in the past (halons) and those halocarbons now being commercialized (HFCs, HCFCs, and perfluorocarbons). We refer to these non-halocarbon materials as "compounds of Main Group Elements." Herein we discuss projects sponsored by the Department of Defense Strategic Environmental Research and Development Program (SERDP) under the Next-Generation Fire Suppression Technology Program (NGP) to explore these two paths. The initiation of this work was discussed at the Halon Options Technical Working Conference 1998.