A: Hydrogen Sulfide is a colorless, transparent gas with a characteristic rotten-egg odor at low concentrations. It is not detectable by odor at high concentrations. As the level of H2S increases, the sense of smell is lost!
Hydrogen Sulfide is a naturally occurring gas mixed with natural gas or dissolved in the oil or brine and released upon exposure to atmospheric conditions.
ACGIH 2017 recommendations are as follows for Threshold Limit Values for H2S:
A Short Term Exposure Limit (STEL) is a TLV(R) based on a 15 minute average.
Short Term Exposure Level - STEL (15 min Average) - 5.0ppm
Long Term Exposure Level -TWA (8 hr average) - 1.0ppm