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H2S Gas

by Morgan Hunter

 Facts about H2S aka “sour gas” 

  • 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