Hydrogen Sulphide Awareness

Under the COSHH Regulations, the long-term exposure limit for hydrogen sulphide is 5 ppm averaged over an 8-hour reference period, and the short-term exposure limit is 10 ppm averaged over a 15-minute reference period.^[1][2]

Hydrogen sulphide is heavier than air (so it accumulates in low spaces), it is flammable, and it burns with a blue flame.

• 0–10 ppm — you may detect a "rotten egg" smell, but this can disappear after a time as your sense of smell is damaged.
• 50–100 ppm — may lead to eye damage.
• 320–530 ppm — may result in pulmonary oedema (fluid in the lungs) with the possibility of fatal consequences.

Work in areas where personnel may be exposed to H₂S requires waterproof, chemical-resistant coveralls, gloves and boots, and protective goggles — together with respiratory protective equipment (RPE).

• Fixed detectors are placed strategically around the installation and initiate toxic-gas alarms to the bridge.
• Portable detectors include hand-held sampling detectors used for background monitoring of H₂S levels.
• Personal detectors are worn by personnel and must be within the user's breathing zone.

RPE must be checked before use (check the air lines for air-supplied breathing apparatus) and examined and tested thoroughly at least every month.

Employers must provide means of detecting, monitoring and protecting personnel from exposure; establish H₂S contingency plans and ensure emergency escape and evacuation arrangements are in place; and ensure defined occupational exposure levels are not exceeded. Employees must co-operate with the ship's Master and follow company procedures at all times, and use the protective equipment provided as instructed.

Fuel tanks should be checked for H₂S before bunkering, during bunkering and after bunkering. Where there is a potential risk of exposure to significant levels of H₂S on oil and chemical tankers, the ship operator or owner is required to assess the risk, put a contingency plan in place and manage the identified risks.

• Long-term limit 5 ppm (8-hour); short-term limit 10 ppm (15-minute).
• H₂S is heavier than air, flammable, and burns with a blue flame.
• 0–10 ppm: rotten-egg smell that fades as smell is damaged; 50–100 ppm: eye damage; 320–530 ppm: pulmonary oedema, potentially fatal.
• PPE: chemical-resistant coveralls, gloves, boots, goggles, plus RPE.
• Detectors: fixed (alarm to bridge), portable (background), personal (breathing zone). Test RPE at least monthly.
• COSHH: employer monitors and plans; employee co-operates and uses PPE as instructed.
• Check tanks before, during and after bunkering; tanker operators must assess and manage the risk.

1. Control of Substances Hazardous to Health (COSHH) Regulations 2002 (UK) — assessment, control and contingency planning for hazardous substances.
2. HSE EH40/2005 — Workplace Exposure Limits (long-term 5 ppm / 8 h; short-term 10 ppm / 15 min for hydrogen sulphide).