813 Construction Worksite Safety

Identifying Permit Spaces

The employer must ensure that a competent person evaluates each confined space to determine whether it is a permit-required confined space (permit space). If the entry employer can answer "yes" to one or more of the following questions, the space is a permit space.

Does the space contain or have the potential to contain a hazardous atmosphere?

Most deaths and injuries in confined spaces result from atmospheric hazards such as insufficient oxygen and toxic or flammable chemicals. The competent person must test and evaluate the space for the following hazards before workers enter the space:

• Oxygen deficiency (concentration less than 19.5 percent) or excess (concentration above 23.5 percent).
• Concentration of any flammable gas, vapor, or mist in excess of 10 percent of its lower explosive limit (LEL):
• Airborne combustible dust at a concentration equal to or greater than its LEL.
• Atmospheric concentration of any substance that can cause death, incapacitation, impairment of ability to self-rescue, injury or acute illness.

Does the space contain a material with the potential to engulf an entrant?

Engulfment means the surrounding and effective capture of a person by a liquid or finely divided (flowable) solid substance that can be aspirated to cause death by filling or plugging the respiratory system or that can exert enough force on the body to cause death by strangulation, constriction, or crushing, or the substance suffocates the individual.

The competent person must consider whether any liquid or flowable solid (such as sand) could enter the space. Any pipe or manhole in an operating water or sewer system in which a worker works is a confined space that could potentially engulf an entrant and must be treated as a permit space.

Does the space have an internal configuration such that an entrant could be trapped by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross section?

An area of a confined space with a small cross section can develop a hazardous atmosphere if ventilation is inadequate. In addition, a space of this configuration could prevent an injured worker from escaping the space and add to the difficulty of rescuing the worker.

Does the space contain any other recognized serious safety or health hazard(s) that pose an immediate danger to a worker’s life or health or would impair the worker’s ability to escape from the space in the event of injury?

Hazards that the competent person should consider include fire and explosion hazards, the presence of mechanical, electrical, hydraulic and pneumatic energy, temperature extremes, radiation, noise, corrosive chemicals, and biological hazards (such as venomous animals or insects).

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