What are the risks of sour gas?
H2S is toxic to humans and animals at very low concentrations. At concentrations between 10 – 750 ppm H2S becomes increasingly toxic. It is deadly to humans in concentrations ofgreater than 750ppm. Most people can smell the distinctive ‘rotten eggs’ odour of the gas at concentrations between 0.1 and 0.3 ppm. Atconcentrations of 20 ppm or more, people may begin to experience slight discomfort in the eyes and nasal passages, and workers are required to wear breathing apparatus. At higher levels, around 100 ppm, the gas becomesmore dangerous because it quickly numbs the sense of smell. Health effects such as dizziness and slight respiratory difficulties begin with exposure for an hour at 150 ppm, and fatalities can result from exposure to levels above 750 ppm unless the person is immediately evacuated and resuscitated.
