Different types of confined spaces exist, and some of them pose dangers that necessarily require the use of a permit. A confined space, according to OSHA 29 CFR 1910.146 “Permit-required confined spaces”, is a space that is sufficiently large and configured to enable an individual to access in full body to execute project tasks, the point of entry and/or exit is limited or constrained, as in the case of a vessel or tank, and the space was not constructed for employee occupancy for an extended period of time.

Figure 14: Workspace limited to one tank in the chemical area.

The main risks of entering a permit-required confined space can be described, according to OSHA, as follows:

  • Exposure to hazardous atmosphere.
  • Exposure to materials with potential for engulfing.
  • Possible entrapment or asphyxiation.

OSHA's 1910.146 standard lists certain preventative steps that apply to both the primary employer and any contractor doing asset inspections, including but not limited to:

  • Pre-entry hazard evaluations.
  • Specification of acceptable entry conditions.
  • Verification of the conditions as acceptable.
  • Coordination of entry operations.
  • Isolation of the confined space.
  • Usage of forced ventilation.
  • Purging, inerting, flushing, or ventilating the permit space as necessary to eliminate or control atmospheric hazards.
  • Provision of personal protective equipment, lightning equipment and communication equipment for the person entering the confined space.