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14. Hot Work | Confined Spaces Guideline

Disclaimer: This resource has been prepared to help the workplace parties understand some of their obligations under the Occupational Health and Safety Act (OHSA) and regulations. It is not legal advice. It is not intended to replace the OHSA or the regulations. FOR FURTHER INFORMATION PLEASE SEE FULL DISCLAIMER

What is "hot work"?

"Hot work" is work that could produce a source of ignition, such as a spark or open flame. Examples of hot work include welding, cutting, grinding and the use of non-explosion proof electrical equipment.

What is "cold work"?

"Cold work" is work that cannot produce a source of ignition. Examples of cold work include valve adjustment and brush painting.

What precautions are required to perform hot work in the presence of a combustible dust or mist?

The space should be ventilated or purged to reduce the combustible dust or mist airborne concentration to a level below that which may create a hazard of explosion.

If ventilation or purging cannot reduce the combustible dust or mist airborne concentration to a level below that which may create a hazard of explosion, the space must be rendered inert by adding an inert gas and be continuously monitored to ensure the atmosphere remains inert. Workers must wear adequate respiratory protective equipment and adequate equipment to allow persons outside the confined space to locate and rescue them, if necessary.

What precautions are required to perform hot work in the presence of an explosive or flammable gas or vapour?

In order to perform hot work in the presence of an explosive or flammable gas or vapour, the following precautions must be taken:

  1. The space is purged and continuously ventilated to maintain an atmosphere of less than 5% of the LEL;
  2. The space is purged and continuously ventilated to maintain an oxygen concentration of less than 23%;
  3. The atmosphere in the confined space is continuously monitored;
  4. The entry permit includes adequate provisions for hot work and details the appropriate measures to be taken; and
  5. An adequate warning system and exit procedure are in place to provide adequate warning and allow safe escape if the levels in a) or b) above are exceeded. It is good practice to incorporate a safety factor that provides for adequate warning should the levels be approached.

Alternately, the space must be rendered safe by inerting with an inert gas and continuously monitoring the atmosphere, particularly with regard to oxygen concentration. Workers must wear adequate respiratory protective equipment and equipment to allow persons outside the confined space to locate and rescue them, if necessary.

May I perform hot work in a confined space if there are no flammable gases, vapours or dusts present?

Yes, as long as all the appropriate measures for confined space entry have been taken.

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