Symptoms of H2S exposure and exposure limits

You’re walking to the next spot on your maintenance route when you get a whiff of rotten eggs that makes your nose hairs stand on end. It only lasts for a second, so you don’t think much of it. What you didn’t realize was that an unseen gas paralyzed your nose.

You’ve completely lost your guiding sense, and you’re about to walk into a cloud of invisible poison. Then you stop and remember your training. By recognizing the symptoms of hydrogen sulfide exposure, you can prevent disaster in the workplace.

Symptoms of acute exposure include nausea, headaches, delirium, disturbed equilibrium, tremors, convulsions, and skin and eye irritation. Inhalation of high concentrations of hydrogen sulfide can produce extremely rapid unconsciousness and death. Exposure to the liquified gas can cause frostbite injury.

Worker Exposure Limits (Enforceable)

• General Industry: 29 CFR 1910.1000 TABLE Z-2, Toxic and hazardous substancesExposures must not exceed 20 parts per million (ppm) (ceiling) with the following exception: if no other measurable exposure occurs during the 8-hour work shift, exposures may exceed 20 ppm, but not more than 50 ppm (peak), for a single time period up to 10 minutes.
• Construction: 29 CFR 1926.55 Appendix A, Gases, vapors, fumes, dusts, and mistsSets exposure limit of 10 ppm (15 mg/m³) time-weighted average (TWA)
• Shipyard: 29 CFR 1915.1000 Table Z, Air contaminantsSets exposure limit of 10 ppm (15 mg/m³) TWA

Other Exposure Limits for Hydrogen Sulfide: NIOSH Recommended Exposure Limit (REL): 10 ppm, 10-minute ceiling Concentration considered immediately dangerous to life and health (IDLH): 100 ppm

ACGIH^® recommends a threshold limit value (TLV^®) of 1 ppm as an 8-hour time weighted average (TWA) and a short-term exposure limit (STEL) of 5 ppm.