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.

September 21, 1995

The Honorable Bill McCollum
605 East Robinson Street, Suite 650
Orlando, Florida 32801

Dear Congressman McCollum:

We have received Mr. Bennett's letter dated July 24, 1995, regarding the use of explosion proof certified equipment inside of pipes and manholes. In the letter, Mr. Bennett addressed four questions to the Occupational Safety and Health Administration (OSHA) for response; all related to conducting television inspections inside pipeline(s). The letter also included a copy of a previous letter of interpretation issued by OSHA's Director of Compliance Programs concerning the application of the hazardous (classified) location standard (29 CFR 1910.307) and the permit required confined space entry standard (29 CFR 1910.146) to pipeline inspections. The issues raised by Mr. Bennett's questions also seem to fall under one or both of those same two standards, depending on whether employees enter the area as a confined space or could be adversely affected while working outside the pipeline with the cameras placed in the pipeline.

The responses to the questions raised are set forth below.

Question 1: Do you believe the use of explosion proof certified equipment inside the pipe and manhole only provides any appreciable increased safety factor?

Reply: Sewers and excavations containing sewers are normally considered as locations which may contain hazardous atmospheres. Both the Permit-required confined spaces standard (29 CFR 1910.146) and Subpart P--Excavations in the construction standard recognize sewers and excavations containing sewers as areas where adequate precautions are to be taken to prevent employee exposures to flammable gases. The general requirements for excavation require the taking of adequate precautions to prevent employee exposure to an atmosphere containing a concentration of a flammable gas in excess of 20 percent (29 CFR 1926.651(g)(1)(iii)). The Permit-required confined spaces standard includes "flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit" and "airborne combustible dust at a concentration that meets or exceeds its LFL" in the definition of a hazardous atmosphere.

The failure to use equipment and associated wiring approved for the hazardous location could increase the likelihood of an accident. Intrinsically safe equipment and associated wiring approved as intrinsically safe shall be permitted in any hazardous (classified) location for which it is approved (29 CFR 1910.307).

Questions 2 & 3: How many wastewater pipeline explosions have occurred in the U.S. that are attributable to television inspection? How many were reported during the hearings associated with 29 CFR 1910.146?

Reply: Although OSHA has a requirement for reporting of work-related incidents resulting in the death of an employee or the in-patient hospitalization of three or more employees (29 CFR 1904.8(a)) and for logging lost time from workplace injuries (29 CFR 1904.2), OSHA has no requirements for reporting of explosions in wastewater pipelines and has not tracked the frequency of such accidents. Accidents resulting from pipeline inspections are, therefore, likely to go unreported to OSHA, unless injuries or fatalities are incurred.

[This document was edited on 3/5/2004 to strike information that no longer reflects current OSHA policy. Please see the revised Injury and Illness Recordkeeping Standard, 1904 on OSHA's
Recordkeeping Page.]

Question 4: If safety is really a factor, why is the use of certified equipment only required by one wastewater utility, worldwide (UK), and why did that utility purchase the inspection services from their wholly owned subsidiary?

Reply: The hazardous (classified) locations standard (29 CFR 1910.307) covers the requirements for electric equipment and wiring in locations which are classified depending on the properties of the flammable vapors, liquids or gases, or combustible dusts or fibers which may be present therein, and the likelihood that a combustible concentrations or quantities are present. The employer must be able to demonstrate that the equipment will provide protection from the hazards arising from the combustibility and flammability of vapors, liquids, gases, dusts, or fibers. The National Electrical Code, NFPA 70, contains guidelines for determining the type and design of equipment and installations which will meet this requirement. One method for the employer to demonstrate that equipment used in hazardous (classified) locations meets the requirements of the standard is to use equipment that is certified as intrinsically safe and approved for the hazardous (classified) location (29 CFR 1910.307(b)).

Again, thank you for your inquiry. We appreciate your interest in employee safety and health. If we can be of further assistance, please contact [the Directorate of Enforcement Programs at (202) 693-2100].


Joseph A. Dear
Assistant Secretary

[Corrected 3/5/2004]