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LEGISLATIVE INTERPRETATIONS

OCCUPATIONAL HEALTH AND SAFETY ACT

Performing Cold Work in a Confined Space

Topic: Performing Cold Work in a Confined Space Issued By: V.P.,WorkSafe Services
Statute: Regulation 91-191 Date Issued: September 8, 1997
Section: 267 Date Revised:

267(1) An employer shall not permit an employee to enter or remain in a confined space where the concentration of an airborne chemical agent or mixture of chemical agents or airborne dust in the confined space exceeds 50% of the lower explosive limit of the chemical agent or mixture of chemical agents or dust.

267(2) Where the concentration of an airborne chemical agent or mixture of chemical agents or airborne dust in a confined space does not exceed 50% of the lower explosive limit, an employer shall ensure that:


    (a) explosion proof lighting is used, and

    (b) the only work performed by the employee in the confined space is that of cleaning or inspecting and is of such nature that it does not create any source of ignition.

267(3) Where the concentration of an airborne chemical agent or mixture of chemical agents or airborne dust in a confined space does not exceed 10% of its lower explosive limit an employer shall ensure that:

    (a) explosion proof lighting is used, and

    (b) the only work performed in the confined space is cold work using non-sparking equipment.

Question:
It isn’t clear in the regulation what type of work is permitted or not in a confined space at different ranges of the lower explosive limit. Specifically, what is permitted and when?

Answer:
Work permitted in a confined space in relation with the lower explosive limit (LEL) detected is as follows:

0% of the Lower Explosive Limit
Hot work such as Oxy-acetylene cutting, grinding or welding in a confined space is only permitted when the LEL is 0%. Of course it will be necessary to monitor constantly for toxic gases and the LEL.

1 – 10% of the Lower Explosive Limit
Cold work is permitted in a confined space provided its LEL does not exceed 10%. Explosion-proof lighting and non-sparking equipment must be used.

11% - 50% of the Lower Explosive Limit
Cleaning or Inspection work is permitted in a confined space provided its LEL does not exceed 50%. Explosion-proof lighting must be used and the nature of the work will be such that it does not create any source of ignition.

51% of the Lower Explosive Limit
Entering or remaining in a confined space is not permitted when it exceeds 50% of the LEL.

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