Is exposure to hydrogen sulfide harmful?

The state standard based on nuisance for outdoor levels of hydrogen sulfide is 30 parts per billion (ppb) averaged over one hour. For short-term exposures below these levels, toxicological health effects are not expected to occur, although strong odors are known to evoke physiological responses, such as headaches and nausea.  However, the symptoms associated with this level of exposure are expected to be temporary. For chronic, long-term exposures, the state standard is 8 parts per billion, which is considered a concentration that provides reasonable protection from odor annoyance in practice.

In February 2016, upon the successful stoppage of the active natural gas leak plume in Aliso Canyon, SCAQMD and CARB established criteria  for typical air quality levels, based on assumed typical pre-leak concentrations.  For hydrogen sulfide, any measurement at or below 10 ppb by any SCAQMD or CARB measurement beyond the fence line of the Aliso Canyon facility (including surrounding communities) is a factor to consider for residential occupancy.  30 ppb hydrogen sulfide (1-hr average) is the state standard for this air toxic.