H2S concentration for human contact time (Maddox, 1982).
|Period of exposure||Parts of H2S per million parts of air (ppm)|
|Maximum allowable concentration for prolonged exposure||10|
|Slight symptoms after exposure of several hours||70-150|
|Maximum concentration that can be inhaled for 1 h without serious consequences||170-300|
|Dangerous after exposure of 30 min to one hour||400-500|
|Fatal in exposure of 30 min or less||600-800|