Toxicological Properties of Halon Substitutes

Abstract

Halon fire extinguishing agents are used throughout the world to protect valuable electronics, oil and gas production operations, military systems, as well as a number of other critical facilities. Unfortunately, halons deplete stratospheric ozone, causing destruction at 3 to 16 times the rate of CFC-11 (a common refrigerant). As a consequence, the production of halons was prohibited on December 31, 1993 by an international treaty, the Montreal Protocol. This ban on halon production resulted in a search for replacement chemicals for firefighting and explosion protection applications. Replacements must satisfy the following three criteria in order to be successful candidates: effectiveness, cleanliness, and environmental acceptability (low ozone depletion and global warming potentials). It is also necessary that a replacement agent be as non-toxic as possible relative to possible exposures and generate minimal toxic and corrosive decomposition products during the suppression event. Herein, the toxicological aspects of halon replacements are discussed. The specific toxic endpoints of concern for halocarbon candidates, as well as the kinds of toxicity testing required for halon replacements, will be addressed. The paper will also provide a summary of the toxicological properties for the most promising near term halon replacements. Associated decomposition product formation will be briefly discussed. Toxicity ConsiderationsConsiderations of the short-and long-term health hazards of exposure are of key importance when deciding which compounds hold potential for use in explosion and fire protection. Human and animal research indicates several principal adverse health effects caused by halocarbons. They can stimulate or suppress the central nervous system (CNS) to produce symptoms ranging from lethargy and unconsciousness to convulsions and tremors (7). Halocarbons can cause cardiac arrhythmias and can 1

The development of environmentally acceptable fluorocarbons

“…Acute toxicity. A 4 h exposure of rats to levels of 110,000 and 800,000 ppm of HFC 227ea did not cause mortality (Skaggs et al 1995).…”

“…Exposure of Wistar rats to levels of 50,000 ppm of HFC 227ea, for 6 h/day, 5 days/week for 4 weeks did not result in any observable signs of toxicity. It was also reported that exposure of rats to a level of 105,000 ppm did not cause adverse effects (Skaggs et al 1995).…”

“…Cardiac sensitization. The potential of HFC 227ea to sensitize the heart to epinephrine (adrenaline) was investigated using beagle dogs (Skaggs et al 1995). Exposures were conducted for 5 min at which time the dogs were given an injection of adrenaline just below the threshold required to produce a spontaneous arrhythmia.…”

Computational Study on Toxic Gases Released From Compartment Fires Suppressed With Halogenated Agents

“…Smoke and CO induce high levels of carboxyhemoglobin in the bloodstream, resulting in incapicitation or death. Approximate lethal concentrations (ALCs) for a 15-min exposure to HBr, HF, and COF 2 are 4750, 2500, and 1500 ppm, respectively (Skaggs et al 1995). With the advent of sophisticated models of enclosure fires and detailed reaction mechanisms, more attention is now being paid to the prediction of the formation rates of toxic compounds in fires.…”