OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

August 11, 1993

Mr. W.H. Butterbaugh, CAE Director
Regulatory Affairs NPGA
Suite 340 4301
North Fairfax Drive
Arlington, Virginia 22203

Dear Mr. Butterbaugh

Thank you for your letter of July 1, in which you asked for a clarification of the definition of a permit-required confined space (permit space).

The precise definitions you seek are found in the standard (relevant portion attached.)

To paraphrase, a confined space is a space that:

(1) Is large enough and so configured that an employee can bodily enter and perform assigned work; and

(2) Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry); and

(3) Is not designed for continuous employee occupancy.

In addition to the criteria listed above, a permit-required confined space (permit space) means a confined space that has one or more of the following characteristics:

(1) Contains or has a potential to contain a hazardous atmosphere;

(2) Contains a material that has the potential for engulfing an entrant;

(3) Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward to a smaller cross-section; or

(4) Contains any other recognized serious safety and health hazard.

Each situation must be measured against these criteria to determine if it is a permit-required confined space. The same space could change its status based on its contents or ventilation. If the crawl spaces and basements, about which you are concerned, fall within these parameters, they are covered; otherwise this standard does not apply. The purpose of the standard is to protect those workers who must enter permit spaces.

Thank you for your concern.


Raymond E. Donnelly, Director
Office of General Industry
Compliance Assistance