The Bureau of Safety and Environmental Enforcement (BSEE) issues regular Safety Alerts. The May 22nd 2023 Alert is to do with the unexpected presence of hydrogen sulfide (H2S) at offshore facilities. They report a significant number of incidents to do with H2S in supposedly gas-free locations. They say,
Although H2S is mostly associated with production from sour petroleum reservoirs, H2S can also form in low-oxygen environments from microbial activity during the decomposition of organic material, or by microbial reduction of sulfates.
With regard to the incidents that the agency has investigated, there have been no injuries.
The following is from our book Offshore Safety Management.
Hydrogen sulfide is a highly toxic, colorless, flammable gas with a pungent odor at low concentrations. (Most texts state that hydrogen sulfide smells like rotten eggs, but, with modern refrigeration, it is probably more apropos to state that rotten eggs smell like hydrogen sulfide.) Exposures to H2S at concentrations as low as 600 parts per million (ppm) can cause death in a matter of minutes due to paralysis of the respiratory system. Because H2S oxidizes rapidly in the body there are normally no permanent effects from acute exposure if the victim is rescued promptly and resuscitated before experiencing prolonged oxygen deprivation.
Despite its characteristic odor, the sense of smell cannot be relied upon to detect the presence of H2S because the gas rapidly deadens the sense of smell by paralyzing the olfactory nerve at concentrations greater than 100 ppm. Also, H2S is sometimes associated with other materials such as bunker fuel that have odors that could be strong enough to mask the H2S.
