Setting occupational exposure limits for HFO refrigerants: understanding the process.

An important part of the evaluation of new refrigerants is the determination of an appropriate occupational exposure limit (OEL). For example, an independently derived OEL is required for ASHRAE refrigerant safety classification, which in turn influences allowable use conditions (i.e., through building codes). The OEL development process begins with a review of an informative set of toxicity testing data, moves to the identification of the most sensitive, relevant health effect and is completed by the application of appropriate assessment factors. This paper also discusses the use of exposure limits for short term vs. repeated exposures, the minimum toxicity data set required, and the current understanding of the toxicity of hydrofluoroolefins.