Use of the Reciprocal Calculation Procedure for Setting Workplace Emergency Action Levels for Hydrocarbon Mixtures and their Relationship to Lower Explosive Limits

摘要

This paper proposes a novel use of the reciprocal calculation procedure (RCP) to calculate workplace emergency action levels (WEALs) for accidental releases of hydrocarbon mixtures. WEALs are defined here as the concentration in air that area monitors should alarm at to provide adequate warning and be sufficiently protective of health to allow at least enough time to don respiratory protective equipment (RPE) and escape. The rationale for the approach is analysed, and ways of defining suitable substance group guidance values (GVs) for input into the RCP are considered and compared. WEAL GVs could be based on: 3× RCP GVs (i.e. using the 3× rule), the 5× RCP GVs (i.e. using the 5× rule for calculating ceiling values), emergency exposure limits, or immediately dangerous to life or health values (IDLHs). Of these, the method of choice is to base WEAL GVs on health-based IDLH values, which were developed for emergency situations in the workplace. However, IDLHs have only been set for 11 hydrocarbons, so the choice of GVs is also informed by comparison with possible GVs based on the other approaches.