Confined spaces containing potentially hazardous atmosphere need to be tested prior to entry, and on-going ventilation and testing procedures must be utilized to ensure that the space remains safe for occupancy for the entire duration of the entry.
Recently lowered exposure limit guidelines for H2S, SO2 and NO2 have forced many instrument users to revisit where to set the alarms in their atmospheric monitors.
Failure to periodically test and document the performance of your atmospheric monitors can leave you open to regulatory citations or fines, as well as increased liability exposure in the event that a worker is injured in an accident.
In the past, the most widely recognized occupational exposure limits for hydrogen sulfide (H2S) have referenced an 8-hour TWA of 10 ppm, and a 15-minute STEL of 15 ppm. In February 2010, the American Conference of Governmental Industrial Hygienists (ACGIH®) adopted a new threshold limit value (TLV®) recommendation for H2S, lowering the 8-hour TWA to 1.0 ppm, and the STEL to 5.0 ppm.
In the world of gas detection instrumentation, the expression “better safe than sorry†certainly holds true. Manufacturers and regulatory agencies agree the safest and most conservative approach to assuring instrumentation accuracy is to perform a functional test by exposing the instrument to known concentration test gas before each day’s use.