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 24, 1993

W. A. Mattiford, CSP
Philadelphia Electric Company
2301 Market Street, N1-5
Philadelphia, Pennsylvania 19101

Dear Mr. Mattiford:

This letter is in response to your questions regarding whether air monitoring equipment must be approved by a Nationally Recognized Testing Laboratory (NRTL).

All electrical equipment, except those kinds which no NRTL accepts, certifies, lists, labels, or otherwise determines to be safe, must be "approved", as that term is defined at 29 CFR 1910.399. Except as indicated in the following this means that a NRTL must accept, certify, label, list, or otherwise determine that equipment is safe for it to be considered "approved".

The requirement mandating that electrical equipment be "approved" is set forth at 29 CFR 1910.303(a). Also, OSHA Standard 29 CFR 1910.303(b)(2) requires that "approved" equipment be used in conformance with its approval.

Electrical equipment which no NRTL accepts, certifies, lists, labels, or determines to be safe is acceptable to OSHA under the following if the equipment is inspected or tested by another Federal Agency, or by a State, municipal, or other local authority responsible for enforcing occupational safety provisions of the NEC and found in compliance with the provisions of the NEC as applied to Subpart S of 29 CFR 1910 standards.

Custom made equipment which is designed, fabricated for, and intended for use by a particular customer does not have to be approved if it is determined to be safe for its intended use by its manufacturer. The determination must be made on the basis of test data that the employer keeps and makes available to the Assistant Secretary of Labor for OSHA.

In summary then if there are ten different models of a particular kind of equipment, but only one of them is accepted, certified, listed, labeled or otherwise determined to be safe by a NRTL only that one would be considered to be "approved"; unless of course it is custom made equipment.

Only those entities that have applied and been approved pursuant to the requirements of 29 CFR 1910.7 are considered to be a NRTL. Recently the "Canadian Standards Association" was the first foreign laboratory approved as an NRTL. Enclosed find a copy of a directive that discusses NRTLs.

Please note that even if a piece of equipment is not required to be approved, it still may not be used if it poses a hazard to employees. For example, if it presents an ignition hazard it cannot be used.

If you require any information regarding this matter, please contact John McFee of my staff at (215)596-1201.


Linda R. Anku
Regional Administrator