Gas Detection

14 Jul , 2021

Gas testing is done to ensure that are no dangerous gases are present before starting work that may create a risk to the worker. Gas testing should be done as part of your hazard assessment process and done periodically thereafter to ensure that the workers breathing atmosphere is within limits prescribed by Occupational Health and Safety Rules and Regulations, policies, and procedures prior to the start of any work. 

Gas Monitors

Personal Monitors - are intended for personal safety.  They are worn by workers as personal protective equipment.  Most personal monitors are designed to detect H2S.

Multi Head Monitors are intended for personal and crew safety. They are used when detecting a specific gas usually H2S (as per installed sensors – Max 5) as well as % oxygen (deficient or enriched), LEL (Combustible Gases) and CO2 (Carbon Monoxide).

Specialty Monitors- Sample Draw Volumetric Pumps or Continuous Electronic Monitors draw a measured sample of gas through a detector tube. Detector tubes can be used to test over 150 different types of gases. Detector tubes are very gas specific.

Fixed Monitors – are permanently installed sensing heads that are installed throughout a plant site wherever 24-hour gas surveillance is required. The sensing heads will be connected to a control room where operators can monitor remotely.

For all type of gas testing, you should begin by checking for current calibration, bump the monitor before use to ensure it is functioning accurately and has the correct alarms set for the site you are working at as this may vary by client.

All workers that are completeing gas detection should be trained and deemed competent to complete the task. 

Gas testing for entry into a confined space must be carried out by a qualified safety watch or operations personnel with a current Confined Space entry certificate.


Atmospheric Hazards & Exposure Limits

Occupational Health & Safety Regulations stipulate that gas testing is required to ensure that air quality in the workplace is within acceptable limits for

  •                 Oxygen levels in air
  •                 Combustible or Explosive Gases
  •                 Toxic or Poisonous Gases

Effects of Oxygen Enriched or Deficient Atmospheres

Oxygen Concentration


23% and Above

Increased flammability of materials






Minimum for safe work conditions

18% and Less

Increased breathing, impaired thoughts

 14% and Less

Impaired judgment, fatigue, poor coordination

10% and Less

Sudden collapse and unconsciousness, death


Toxic Gases and Vapours

Worker Exposure Limits OEL (Occupational Exposure Limit)


8 Hour OEL

15 Min OEL

Ceiling or Max





Hydrocarbon Intoxication




Carbon Monoxide




 See Schedule 1 Chemical Substances of Alberta OH & S Code for additional Hazards.

The potential for the development of these hazardous conditions is affected by

  • ·         Physical nature of the space
  • ·         Work being performed.
  • ·         Processes associated with the space.
  • ·         Products used or produced in conjunction with the space.
  • ·         Natural processes (decomposition, oxidization, absorption etc.)
  • ·         External sources of contamination

Workers using multi head or personal monitors will be required to bump test their monitors every day prior to commencing work. Multi Head Monitors require a valid calibration and re-calibration every 3 months or as per manufactures specification.


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