Q: What is H2S?

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 2008 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) - 15ppm

Long Term Exposure Level -TWA (8 hr average) - 10ppm


Exposure Level (ppm) Physiological Response to H2S:
10 ppm Beginning eye irritation
50-100 ppm Slight conjunctivitis (bloodshot eyes) and respiratory tract irritation after 1 hour exposure
100 ppm Immediately Dangerous to Life and Health.
Coughing, eye irritation, loss of sense of smell after 2-15 minutes.
Altered respiration, pain in the eyes and drowsiness after 15-30 minutes followed by throat irritation after 1 hour.
Death may occur within the next 48 hours.
200-300 ppm Marked conjunctivitis and respiratory tract irritation after 1 hour of exposure
500-700 ppm Loss of consciousness and possibly death in 30 minutes to 1 hour
700-1000 ppm Rapid unconsciousness, cessation of respiration and death
1000-2000 ppm Unconsciousness at once, with early cessation of respiration and death in a few minutes.
Death may occur even if individual is removed to fresh air at once.

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