Safe Work Practices > Hydrogen Sulphide

Date Reviewed: February 15, 2023

Hydrogen Sulphide (H2S) is a naturally occurring, colourless and odourless (at higher concentrations) gas that can be highly toxic. In high enough concentrations, it can paralyze the breathing control centre in the brain and the respiratory system with one breath. Any employees required to work in potential H2S atmosphere, where engineering and/or administrative controls have failed to produce a breathable atmosphere, will be supplied, and required to wear, a self contained breathing apparatus.

Worker Maximum Exposure Limits in Parts Per Million:

•Sask. - Exposure must not exceed concentrations of 10 ppm for more than an 8 hours period as per table 21 of the Sask. OHS Regulations.

•Sask - Exposure must not exceed concentrations of 15 ppm for more than a 15-minute period as per table 21 of the Sask. OHS Regulations.

•MB - Exposure must not exceed concentrations of 1 ppm for more than an 8 hours period.

•MB - Exposure must not exceed concentrations of 5 ppm for more than a 15-minute period.

CHARACTERISTICS / EFFECTS

•Colourless gas

•Smells like rotten eggs at between 1 ppm and approx. 100 ppm. Sense of smell is deadened after this concentration.

•Heavier than air, will settle in low areas, excavations, confined spaces, etc.

•Will readily mix with liquids and then be released when liquids are disturbed.

•Will cause irritation of eyes and throat at approx. 200 ppm.

•Will cause respiratory distress within 2 minutes at 500 ppm.

•Will cause immediate respiratory arrest at 1000 ppm.

•Flammable properties 4% LEL and 46% UEL.

EXPOSURE ACUTE HEALTH EFFECTS

•Less than 1 ppm - You can smell it.

•10 ppm - No known adverse health effects for most people. Respiratory protection is required beyond this level.

•20-50 ppm - Eye, nose, throat and lung irritation.

•100-150 ppm - Severe eye, nose, throat and lung irritation. Loss of smell. Exposure duration of 8 hours or more may be fatal.

•200-300 ppm - Headaches and drowsiness. Prolonged exposures of several hours may cause lungs to fill with fluid.

•300-500 ppm - May cause unconsciousness and death in 1 to 4 hours.

•500-700 ppm - Knockdown may be fatal within 1 hour at this level of exposure.

•Greater than 700 ppm - Immediate knockdown may be fatal.

EMPLOYEE TRAINING REQUIREMENTS

All employees shall be required to attend an 8 hour H2S Alive training course if they are required to work in areas where this gas may be encountered.

RESCUE
NOTE: No rescue attempt shall take place unless H2S gas measurements are below 500 ppm!

Whenever someone is overcome by H2S or this is suspected, DO NOT RUN INTO THE AREA TO AFFECT A RESCUE. Proceed in the opposite direction, call for help / backup, don breathing apparatus, and then remove the casualty from the area. Only after you and the casualty are free of the affected area can you remove the breathing apparatus and apply artificial respiration. When the casualty exhales, avoid breathing in the exhaled H2S. Any person who has been overcome by H2S shall seek medical attention (no matter what the circumstances) as H2S can turn into Hydro Sulfuric Acid in the lungs and cause pneumonia.

WORK PROCEDURES

•Whenever possible, work with others on a sour lease. This is not always possible, so maintain communication as often as possible via radio when on a sour lease.

•Work up-wind of the operation as much as possible.

•Attach a vent hose and rout it away and downwind from the operation and truck when handling potentially sour liquids.

•Avoid enclosed areas, H2S process buildings, tanks trenches or any other place that H2S may settle, as much as possible. Treat these areas as potential confined spaces when on a sour lease.