March 29, 2023

Mr. David Hoffman
28494 Westinghouse Place
Valencia, California 91355

Dear Mr. Hoffman:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA) concerning the application of OSHA standards when an employer is using the "Focused Electrode Leak Locator" (FELL) noted in your letter. This constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. We apologize for the delay in our response. Your questions are paraphrased below, and our responses follow.

Scenario: You state that the FELL device tests for possible cracks in pipes for mainline and lateral gravity flow storm sewers, sanitary sewers, and combined sewers by emitting electric current inside the sewer line, possibly in the presence of flammable gases, and receiving current outside the sewer lines. You also state that there is an explosion hazard connected to the use of the FELL device in the manner you describe, and that the device is used in a Class 1, Division 1 location under OSHA's Electrical Standard at 29 CFR 1910 Subpart S ("Subpart S").¹ Finally, it appears, based on an illustration you included with your inquiry, that the FELL device is powered by a portable generator that is brought to the test site via an "Electro Scan Inspection Van."

OSHA makes no assurance that the FELL device operates in the manner you say it does or is effective for testing for possible cracks. OSHA's response to your inquiry should not be taken out of context or given a broader application than was intended. Consistent with long-standing policy, OSHA does not approve or endorse particular products.

In addition, OSHA cannot give you definitive answers to your questions, which are based on assumptions that may or may not be true. Since OSHA has not examined the FELL device you describe and does not know the precise nature of the environments in which the device would operate, OSHA cannot determine the applicability of, and compliance with, the OSHA standards about which you inquire. Determinations of this nature would need to take into account all factors pertaining to the use of the FELL device at a particular worksite with respect to employee safety and health. This would need to include an evaluation, through direct observation, of employee work practices and all conditions in the workplace. Therefore, OSHA's responses to your questions, which obviously cannot take into account the additional factors cited above, does not guarantee compliance with the requirements of OSHA's standards, and the utility of OSHA's responses may be, and likely is, limited.

Finally, your questions, which OSHA paraphrases below, center on the Design Safety Standards for Electrical Systems (29 CFR 1910.302 thru 1910.308), which are contained in Subpart S, and, for one question, the applicability of OSHA's Permit-Required Confined Spaces Standard, 29 CFR 1910.146. While OSHA's responses are limited to discussion of those standards, employers must comply with all applicable OSHA standards (e.g., the Safety-Related Work Practices requirements in Subpart S, 29 CFR 1910.331 thru 1910.335), and not just those discussed in this letter, as well as the Occupational Safety and Health Act's General Duty Clause, 29 USC 654(a)(1).

Question 1: Are we correct in our understanding that, in order to be compliant with OSHA regulations, this FELL equipment be:

(a) NRTL certified, listed or labeled for the Class I, Division 1 location usage;
(b) compliant with National Electrical Code (NEC)/National Fire Protection Association (NFPA) 70;
(c) compliant with 29 CFR 1910.307(c)(1);
(d) compliant with 29 CFR 1910.307(c)(2); and
(e) compliant with any other safety guideline for similar equipment in order to provide protection to employees from the hazards arising from the use of this equipment?

Response 1:

(a) Assuming for the purpose of responding to your question that the system you describe is an electric utilization system covered by the Design Safety Standards for Electrical Systems in Subpart S (see 29 CFR 1910.302) and that the test site is a Class 1, Division 1 location, the General requirements in 29 CFR 1910.303 and the Hazardous (Classified) Locations requirements in 29 CFR 1910.307 apply to the FELL device.

The General requirements provide, in relevant part, that "[t]he conductors and equipment required or permitted by this subpart shall be acceptable only if approved, as defined in §1910.399." Section 1910.399 provides in relevant part that "[a]n installation or equipment is acceptable to the Assistant Secretary of Labor, and approved within the meaning of ... subpart S:

(1) If it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory recognized pursuant to § 1910.7; or

(2) With respect to an installation or equipment of a kind that no nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe, if it 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 National Electrical Code, and found in compliance with the provisions of the National Electrical Code as applied in [subpart S]; or

(3) With respect to custom-made equipment or related installations that are designed, fabricated for, and intended for use by a particular customer, if it is determined to be safe for its intended use by its manufacturer on the basis of test data, which the employer keeps and makes available for inspection to the Assistant Secretary and his authorized representatives.²

In addition to the General requirements described above, the Design Safety Standards for Electrical Systems in Subpart S contain a number of specific approval requirements. For example, 29 CFR 1910.307(c), which provides that "[e]quipment, wiring methods, and installations of equipment in hazardous (classified) locations shall be intrinsically safe, approved for the hazardous (classified) location, or safe for the hazardous (classified) location," contains specific approval requirements.

(b) OSHA does not explicitly require compliance with the National Electrical Code, NFPA 70. According to a note to §1910.307(c)(3), that consensus standard contains guidelines employers may use for determining the type and design of equipment and installations that will meet the requirement in §1910.307(c)(3) that equipment be safe for the hazardous location. It should be noted that, per the NEC, equipment in Class I, Division 1 locations generally needs to be approved for the hazardous location or intrinsically safe, and the option listed in §1910.307(c)(3) for equipment to be "safe for the location" would not usually be available for Class I, Division 1 locations. See also https://www.osha.gov/laws-regs/standardinterpretations/2000-02-07.

(c) and (d)

In general, equipment in Class I, Division 1 locations must either be approved for Class I, Division 1 locations or must be approved as intrinsically safe for those locations. (As stated, per the NEC, the option listed in §1910.307(c)(3) for equipment to be "safe for the location" would not usually be available for Class I, Division 1 locations.)

(e) OSHA does not understand and cannot answer your question given its breadth and vagueness.

Question 2: Are we correct in our understanding that when uncontrolled electrical current escapes during the FELL testing process from the pipe being tested, it could place adjacent utility services such as federal utilities, natural gas lines, electrical transmission lines, electrical transmission vaults, fiber optic cable transmission lines in jeopardy of flame ignition?

Response 2: OSHA is unable to answer your question. As stated, OSHA has not examined the FELL testing equipment you described, cannot know the precise nature of the environments in which it would operate, and cannot even determine if the use of this equipment is capable of releasing sufficient energy to pose an explosion hazard. Note that a NRTL would examine such hazards as part of its approval process.

Question 3: Are we correct in our understanding that authorization to perform the FELL test work must be obtained from the owners of adjacent utility services (such as federal utilities, natural gas companies, electrical transmission lines, electrical transmission vaults, fiber optic/cable transmission lines) prior to the test?

Response 3: In certain circumstances, the employer may need to obtain information from those who own, operate, or control the operating procedures for, utilities to determine the conditions and hazards at the worksite and protect employees at the worksite from those hazards. OSHA does not require employers to obtain authorization from these entities to perform work on, near, or with those utilities. However, such authorization may nonetheless be required, for example, by local ordinance, or be necessary for reasons related to liability concerns.

Question 4: Are we correct in our understanding that, in order to be compliant with OSHA regulations, this FELL equipment must be compliant to wet environment electrical standards, 29 CFR 1910.303, and/or similar equipment safety guidelines that provide protection to employees from wet environment electrical hazards arising from the use of this equipment?

Response 4: OSHA is unclear what you mean by the portion of your question referencing "similar equipment safety guidelines that provide protection to employees from wet environment electrical hazards arising from the use of this equipment." However, as stated, assuming for the purpose of responding to your question that the system you describe is an electric utilization system covered by the Design Safety Standards for Electrical Systems in Subpart S (see 29 CFR 1910.302), the General requirements in 29 CFR 1910.303 apply to the FELL device. Note that § 1910.303(b)(6) provides that "[u]nless identified for use in the operating environment, no conductors or equipment shall be located in damp or wet locations; where exposed to gases, fumes, vapors, liquids, or other agents that have a deteriorating effect on the conductors or equipment; or where exposed to excessive temperatures."

Question 5: Are we correct in our understanding that only explosion proof certified equipment should be used inside the pipe and manhole in order to provide an appreciable increased safety factor?

Response 5: See the response to question 1(c) and (d), earlier.

Question 6: Are we correct in our understanding that while operating the FELL test equipment, a "Permit Required" confined spaces practice and procedure protocol must be followed, under 29 CFR 1910.146, in order to protect any employees who enter and/or are nearby the confined space?

Response 6: Yes. See Appendix E to § 1910.146 for guidance on sewer entry under § 1910.146. See also https://www.osha.gov/laws-regs/standardinterpretations/1996-08-15-0 for additional interpretive guidance.

Finally, please note that the State of California is one of the twenty-eight States or territories that administers its own safety and health program. State-run safety and health programs are approved and monitored by Federal OSHA. Their occupational safety and health standards must be at least as effective as Federal OSHA's standards. However, State Plans may choose to promulgate and enforce requirements, which are stricter than Federal OSHA's requirements. For information regarding California-specific requirements, we recommend contacting the California State Plan directly at the address below:

Cal/OSHA Headquarters
1515 Clay Street, Suite 1901
Oakland, CA 94612
(510) 286-7000
Fax (510) 286-7037

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA's requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA's interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA's website at https://www.osha.gov. If you have any further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.

Sincerely,

Kimberly Stille, Director
Directorate of Enforcement Programs

¹Class I locations are those "in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures." A Class I, Division 1 location is a location: "(i) In which ignitable concentrations of flammable gases or vapors may exist under normal operating conditions; or (ii) In which ignitable concentrations of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (iii) In which breakdown or faulty operation of equipment or processes might release ignitable concentrations of flammable gases or vapors, and might also cause simultaneous failure of electric equipment" (29 CFR 1910.399).

²An installation is "accepted" under 29 CFR 1910.399 "if it has been inspected and found by a nationally recognized testing laboratory to conform to specified plans or to procedures of applicable codes." Moreover, "approved" means "[a]cceptable to the authority enforcing" Subpart S (that is, the Assistant Secretary of Labor for Occupational Safety and Health). The definition of "acceptable" indicates what is acceptable to the Assistant Secretary of Labor, and therefore approved, within the meaning of subpart S.