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Hydrogen Sulfide (H2S)

Quick Reference

What is H2S?

H2S is a gas that is heavier than air. It has the odor of rotten eggs, is flammable, and highly toxic. It may occur at oil and gas facilities and other industrial or agricultural settings where organic matter may be decomposing. Occasionally individuals intentionally produce it in an enclosed space as a method of suicide.

Crew Safety

  1. Staging/Perimeter
    • Small exposures (single room) = 30m
    • Large or unknown exposures = 400m
  2. Additional Resources
    • Fire or on-scene rescue personnel equipped with SCBAs
  3. PPE requirements
    • SCBA with full face mask required for rescue: BCEHS personnel are not to rescue
    • Standard PPE once patient has been rescued
  4. Safely initiating patient contact
    • Patients must be retrieved by rescue personnel and brought to an area known to be free of H2S

Effect on the Patient

When inhaled, H2S rapidly distributes through all tissues, halting aerobic respiration by inhibiting cytochrome-c-oxidase and depleting ATP in the CNS. Low concentrations cause cognitive or psychomotor impairment. High concentrations rapidly cause unconsciousness, apnea, and cardiac arrest. Susceptibility varies widely. Levels tolerated by one person may rapidly kill another. Also irritates mucous membranes.

Patient Decontamination

  • H2S may become entrapped in clothing. Clothes should be removed and bagged.
  • If eye/skin irritation is present, flush effected area with water.

Patient Treatment

  • No specific antidote. Endogenously metabolized and excreted in the urine.
  • Standard ACLS for patients in cardiac arrest.
  • Support of ABC’s as indicated.
  • High-flow oxygen for any patient who was symptomatic at any time.

Safe Transfer of Care

  • H2S can become trapped in clothing. Clothing should be removed to prevent off-gassing.
  • No risk of the patient exhaling H2S and harming health care workers.
  • No isolation or special PPE required once patient is extricated and decontaminated.

Paramedic and Equipment Decontamination

  • Provided the paramedic did not enter the scene no personal decontamination is needed.
  • Provided clothing was removed before transportation no special decontamination required.
  • If clothing was transported with the patient, open ambulance doors and ventilate for 20 minutes.
DPIC Monograph

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Paramedic Specialist Monograph

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Emergency Response Guidebook

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Revision History

Version Date Changes Author
1.0 2026-05-01 Initial version Clinical Hub