BY JEFFREY POST
Each day across North America, a fire department responds to an incident requiring gas detection beyond the limits of a standard four-gas meter. These incidents include but are not limited to unknown odors, confined space and trench rescues, and chemical runs. In a large percentage of these calls, the first-due companies are not specialized hazardous materials units. With the development of regionalized hazardous response assets, although many fire departments now have access to photo ionization detectors (PIDs), they may overlook them as a valuable response tool. An emergency response organization will greatly increase its effectiveness and the level of protection it offers its employees (responders) by more frequently deploying a PID in response. Although some departments have these instruments, their use is shrouded in mystery and wordy user manuals. I offer below a user-friendly training tool to improve responder safety.
A PID measures volatile organic compounds (VOCs), a vast chemical family that includes common chemicals such as gasoline, epoxies and resins, paints, and almost all hydrocarbon chemicals (e.g., alkanes, ketones). A PID will also detect alcohols (e.g., ethanol, isopropanol, methanol) and the odorant mercaptan found in propane and natural gas. Typically, VOCs have a high vapor pressure at ambient temperatures, meaning the liquid is giving off vapor readily, which makes gas detection relatively easy. The main purpose of the PID in these types of spills and releases is to measure the toxicity of the atmosphere—i.e., its threat to responders' health.
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