The most typical toxic gases monitored are carbon monoxide and hydrogen sulfide, but other toxic gases include ammonia, chlorine and hydrogen cyanide (just to name a few). Pre-entry testing is accomplished using a remote sampling pump with external tubing or probes. If the levels in the confined space do not exceed the recommended OSHA minimum limits, the worker can enter the area. Once in the confined space, samples must be taken continuously in four-foot increments in the direction of travel.
Matthew Thiel, General Product Manager, Industrial Scientific Corp.