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What are hot work and cold work permits?

Q:

What are "hot work" and "cold work" permits? Where are they used, and how do they serve safety?

A:

Hot work and cold work permits are both attempts at preventing uncontrolled fires. Hot work involves working with a source of ignition, like sparks or an open flame, in an environment with potentially flammable or explosive atmosphere. Cold work refers to a working situation in which there are no sources of ignition present.

As far as how they serve safety and reduce risk, it's worthwhile taking a look at risk assessments for hazardous areas, which tend to have two phases:

  1. Static assessments: Dealing with the normal process safety aspects and the hierarchy of hazard control (learn more about The Hierarchy of Hazard Control). They are primarily concerned with the equipment, the plant, and the process.
  2. Dynamic risk assessments: Task-specific and performed by appropriately competent personnel immediately prior to, throughout the duration of, and following any specific planned task or intervention.

The first will require identifying any area that could carry a risk of a flammable, explosive, or otherwise harmful atmosphere. Depending on the size of expected release under normal working conditions and the amount of time it is likely to exist, these are normally segregated into different zones of increasing residual or remaining risk.

When a flammable atmosphere is part of the conditions of the work site, the best way to prevent a fire from breaking out is to control the ignition source. This is usually done by installing appropriately designed equipment and issuing the proper training for employees working in the environment.

The permit system allows the work to be carried out safely by specifying everything from the competency of the working party right down to the methodology and tools employed.

The permit also delimits the work being done from operations performed in adjacent areas, so that one does not impact on the other. It also allows for contingency planning and putting sufficient mitigation measures in place to deal with any foreseeable incident arising from planned work.


When in doubt, you can always refer to NFPA 51B, the Standard for Fire Prevention During Welding, Cutting, and Other Hot Work. A hot work program including a permit system, fire watch requirements, designated hot work area requirements, etc., is to prevent fires and losses. All facilities should have some provisions for hot work. Hot work's definition is not limited to locations with potential flammable atmospheres; it is work (burning, welding, grinding, etc.) that is capable of initiating fires or explosions of any combustible and flammable materials and/or atmospheres. For example, hot work taking place inside an office requires all the provisions of a hot work program even though a flammable atmosphere is not expected in an office - there's significant amounts of combustibles and significant potential for fire losses.

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Written by Gary Melrose
Profile Picture of Gary Melrose

Project Manager with experience of delivering complex, multi specialist projects, leading multi discipline project teams to deliver whole lifecycle optimized solutions.

Specific experience in leading various hazard and operability studies to ensure both safety lifecycle (PM 84 and BS EN 61511) and RAM lifecycle (BS 6079 and BS 5760) deliverables are whole lifecycle optimized for current and predicted operational lifecycles.   Full Bio