Guidelines for Hydrogen Sulfide exposure have gone through a major change. Did you know about it? Looks like not many safety professionals in oil and gas did. A survey found that more than half of the professionals contacted did not know that the American Conference of Governmental Industrial Hygienists has recommended a dramatic reduction in the allowable exposure limits. More significantly, three-quarters of the people who did know about the change are not moving very quickly to adopt it.
You can read more about the actual guidelines themselves here, but OH&S Online says the meat of it is that:
(ACGIH) changed its recommended threshold limit values (TLVs) for airborne hydrogen sulfide (H2S) exposure. Previously, the ACGIH recommendation for an eight-hour time weighted average (TWA) exposure limit was a concentration of 10 parts per million and the 15-minute short-term exposure limit (STEL) was 15 ppm. The new recommendations for airborne H2S exposure are a TWA of 1 ppm and an STEL of 5 ppm. While compliance with these recommendations is not mandatory, they were developed from scientific data gathered by ACGIH during several years on the health effects of H2S exposure.
As the article states, the guidelines are not mandatory and the OSHA levels are still higher, but OSHA recently announced an online database of permissible limits, including these new H2S guidelines. This threatens to become a dangerous legal grey area for employers where several limits exist side-by-side with no clear definition of what consitutes “safe” limits.