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.

July 11, 1995

Mr. Alan K. Sefton
Pearpoint, Inc.
72055 Corporate Way
Thousand Palms, California 92276

Dear Mr. Sefton:

This is in response to your letters of June 9, and September 30, requesting Occupational Safety and Health Administration's (OSHA) determination as to what OSHA safety standards are applicable to underground sewer pipeline inspection camera systems which include electric equipment, that is, cameras mounted on electric crawlers, and associated conductors. Your questions and our response follow. Please accept our apology for the delay in responding.

Question 1: Under 29 CFR 1910.146 Appendix D "Sample Permits", sewers are to be treated as a potentially hazardous (classified) location (Class I, Division I, Gas Group C) when personnel are to be present within the structure. Does the same classification continue when personnel are replaced with electrical equipment within the structure?

Question 2: If the sewer is considered a potentially hazardous (classified) location, should it be required to comply with 29 CFR 1910.307?

Question 3: If the sewer is considered a potentially hazardous (classified) location would the accepted classification be as called for in 29 CFR 1910.146 Appendix D "Sample Permits" and NFPA/ANSI 820?

Reply: Your questions seem to center on whether section 1910.146 requires that explosion-proof equipment be used in the sewers described above. This standard only addresses hazards in a permit-required confined space (PRCS) where there is (or could be) an "entry" by an employee into this type of space. As noted above you assume that there is no such entry.

Apart from some duties to barricade or otherwise prevent entry into a PRCS, which is addressed by section 1910.146, the issue of whether explosion-proof equipment must be used in sewers where there is no entry into the sewers is addressed by 29 CFR 1910.307 which is not predicated on entry by employees into such spaces. As long as an employee is exposed to the explosion hazard, section 1910.307 requirements apply. As described in your letter, employees are stationed outside at the manhole entrance to the sewer and could be exposed to the explosion hazard whether the manhole is covered or not. The types of equipment specified in the 1910.307 standard would have to be used when employees are or could be exposed.

By 1910.307(b), electrical installations, including equipment, wiring methods and installation of equipment in classified locations must be intrinsically safe, approved for the hazardous (classified) location, or safe for the hazardous (classified) location. An employer may use these options at a work site when he or she complies with 1910.307 and specifically the requirements in paragraphs (b)(1), (2) and (3) as they apply to the options used.

The national consensus standard of reference (see the note at the end of 1910.307(b)) containing guidelines for determining the classification of electrical installations in hazardous (classified) locations, including sewers, and the equipment and installation requirements in such locations is the National Electric Code, NFPA 70.

If we can be of further assistance, please contact Ron Davies of my staff, telephone (202) 219-8031, extension 110.


John B. Miles, Jr., Director
Directorate of Compliance Programs