How to Characterize Confined Spaces

by Jan 5, 2021Confined spaces

Once the confined spaces in the workplace have been enumerated based on the definition of the regulation respecting occupational health and safety (RROHS), they must be characterized. But how is it done?

Here is some advice to guide you in the process:

First, make sure that the characterization will be done by someone with the proper knowledge, expertise, and training. Once this person has be determined, more information needs to be established about the confined space. E.g.:

  • Its physical dimensions
  • Its contents
  • The need of access
  • The risks present or that could be, for example:
    • Atmospheric hazards
    • Biological hazards
    • Chemical hazards
    • Energy hazards
    • Entrapment
    • Explosions
    • Drowning
    • Burial
    • Falling
  • The severity and probability of an accident occurring due to the risks identified

Once this information is collected, each confined space must be classified according to the National Institute for Occupational Safety and Health (NIOSH). This way, the confined space will be classified according to the potential or existing hazard into 3 distinct classes.

Class A: Immediately Dangerous to Life/Health (IDLH)

  • Including confined spaces where the atmosphere is deficient in oxygen, explosive, flammable or toxic.

Class B: Not IDLH, but dangerous (potential injury, sickness, etc.) if the appropriate measures are not taken.

Class C: Potentially hazardous but where the risks are negligible and that does not require particular preventive measures other than the usual work procedures.

Characterization is a crucial step because it governs what is required for a specific confined space:

  • Safety measures to be taken before each entry
  • Rescue plans
  • Rescue equipment
  • Number of workers
  • Personal protective equipment
  • Collective protective equipment
  • Type of mechanical ventilation
  • Atmospheric detection method
  • And more

When characterization of confined spaces is carried out professionally and methodically, lives are spared. If you need our experts to guide your in your process, contact us so we can assist you.

Tell us about your needs and an expert will answer you!

Intervention Prévention Inc.

Intervention Prévention concentrates its operations in the field of work safety, offering specialized services following Standards CSA Z462 – Workplace Electrical Safety, CSA Z460 – Control of Hazardous Energy: Lock-out and Other Methods, and CSA Z432 – Safeguarding of Machinery.


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