H2S is heavier than air, accumulates in low-lying areas, and may travel along the ground.
The danger with H2S lies in the fact that at higher concentrations, it does not obtain a noticeable odor. At low concentrations the smell is often is described as “rotten eggs”
When unprotected workers, rescue workers, etc. are exposed to high concentrations of H2S it can quickly- almost immediately slip them into unconsciousness. (Hence the term knockdown)
Knockdown is almost immediate when H2S is at, or above 700ppm.
The identification of many of these wells where H2S gas is found has taken place, however “sweet wells,” which contain no H2S, can turn “sour” overnight.
The health risk/effects due to exposure is determined by how much H2S was inhaled. Higher concentration exposures quickly can lead to debilitation, and/or death.
H2S is extremely flammable. When H2S reaches concentrations in the air between 4.0% and 4.6% it will ignite.
S02 gas is a corollary combustion of H2S, and is considered virulent. S02 in all likelihood will be present when H2S is at the cause of the fire.
When employers are choosing equipment that they may anticipate to encounter H2S, it’s critical to remember H2S is highly caustic, and in return, causes metals to become very thin/brittle.
It’s feasible for H2S to cumulate in any low/confined area. Areas can include cellars, mud systems, gas venting systems, pits, and tanks
