I am a client of Allstar Enviro Safety. I told the instructor about my friend who was working in the Oil Sands as a Foreman Scaffolder. Two of his apprentices passed out due to exposure to H2S gas. Without getting respiratory protection, the foreman went to the aid of his fellow workers. Little did he know that they had already passed out from the Hydrogen sulphide exposure. He dragged these men to safety and passed out afterwards.
The foreman spend a lengthy time in the hospital getting better but was told by the physician that he may have taken 10-15 years off his life due to the H2S exposure!
Ryan Verboom Story told July 2014
Additional Safety Knowledge
Understanding H2S — The Basics
Hydrogen sulphide (H2S) is a colourless, flammable gas heavier than air with a characteristic rotten-egg odour at low concentrations. It is produced naturally by anaerobic decomposition of organic matter and is present in sour oil and gas reservoirs, sewer systems, wastewater treatment, pulp and paper operations, tanneries, and manure storage pits. In Alberta’s upstream oil and gas industry it is the single most common atmospheric hazard.
Exposure Concentrations and Effects
- 0.01–1.5 ppm: detectable by smell — the classic rotten-egg odour.
- 10 ppm: Alberta occupational exposure limit (OEL) 8-hour time-weighted average.
- 15 ppm: Alberta 15-minute short-term exposure limit (STEL).
- 50–100 ppm: eye irritation, respiratory discomfort, olfactory fatigue (sense of smell disappears — a dangerous false-safety signal).
- 100 ppm: NIOSH Immediately Dangerous to Life or Health (IDLH) limit.
- 500–700 ppm: loss of consciousness within minutes, respiratory paralysis, death likely without immediate rescue.
- 1,000 ppm and above: single-breath knockdown — instant collapse and death.
Detection and Personal Monitoring
Every worker in a potential H2S atmosphere must carry a personal 4-gas monitor calibrated for H2S detection. Standard alarm setpoints are 10 ppm (low alarm) and 15 ppm (high alarm). Bump testing is required before every shift; full calibration every 30 days minimum. Fixed detection systems with visual and audible alarms are required at facilities with continuous H2S risk.
H2s Knockdown Encounter — Emergency Response
The first response to an H2S alarm is not to investigate — it is to evacuate upwind and uphill (H2S is heavier than air). Muster at the designated point, complete roll call, and notify the incident commander. Rescue attempts require Self-Contained Breathing Apparatus (SCBA), a trained rescue partner, and a documented rescue plan. Attempting rescue without SCBA is the leading cause of secondary H2S fatalities.
Content reviewed by Arliss Levine, CRSP, CHSC — lead safety instructor at Safety Mom · Allstar Enviro Safety Calgary, an Energy Safety Canada Authorized Training Provider.
