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 3, 1993

Ms. Patricia H. Falls
Vice President
Firstline Safety Management, Inc.
P.O. Box 230
Lovettsville, Virginia 22080

Dear Ms. Falls:

This is in response to your February 8 letters requesting interpretation of various Occupational Safety and Health Administration (OSHA) standards. I apologize for the delay in responding to your inquiry.

With regard to whether cord- and plug-connected equipment includes extension cords used between the power supply and the tool when the power supply is a portable generator, please be advised that such extension cords would be considered to be cord-and plug-connected equipment as described in 29 CFR 1926.404(f)(3)(i)(A)

With regard to 29 CFR 1926.404(f)(3)(i) and your question of whether ground-fault circuit interrupters (GFCI's) are required when using portable generators, please be advised that OSHA does not require the use of GFCI's on portable or vehicle-mounted generators of 5kW capacity or less if the output is a two-wire, single-phase system and the circuit conductors are insulated from the generator frame and all other grounded surfaces. (See 29 CFR 1926.404(b)(1)(ii).)

With regard to 29 CFR 1926.404(f)(3)(i) and your question of whether or not a receptacle wiring tester can show if a portable generator is properly grounded, please be advised that the answer is primarily dependent on the configuration of the generator involved. Standard receptacle outlet testers will correctly identify the presence or absence of a properly wired equipment grounding conductor for three-wire, single-phase portable generators (except that some multiple wiring defect combinations cannot be detected). However, such testers will typically indicate the absence of an equipment grounding conductor on two-wire, single-phase portable generators, even when the generator is wired in accordance with OSHA standards. (The reason for this is because two-wire, single-phase portable generators need not have either circuit conductor connected to the equipment grounding conductor at the generator frame. On the other hand, a three-wire, single-phase generator must have its neutral conductor, as well as the equipment grounding conductor, bonded to the generator frame.)

With regard to your policy of instructing companies to comply with the requirements for guarding of low-pitched roof perimeters during the performance of built-up roofing work on roofs with a ground to eave height of 12 feet - 14 feet, please be advised that 29 CFR 1926.500(g) only applies to low-pitched roofs with a minimum ground to eave height greater than 16 feet. Nevertheless, your policy provides sound advice for your clients in dealing with the hazards of falls associated with working near roof perimeters. Although 1926.500(g) does not call for personal protective equipment such as body belts or harnesses for fall distances less than 16 feet, 1926.95 can be cited to address the hazards of falling less than 16 feet provided OSHA can establish both that a reasonable person familiar with the circumstances would have recognized a hazard warranting the use of personal protective equipment and that the use of personal protective equipment is feasible.

[This document was edited on 3/28/2005 to strike information that no longer reflects current OSHA policy. Former paragraph 1926.500(g) was redesignated to 1926.501(b)(10) by the 1994 revision of Subpart M, and the provision was modified. The provision is also impacted by STD 3.1 (12/8/95) "Interim Fall Protection Compliance Guidelines for Residential Construction" and STD 3-0.1A (6/18/99) "Plain Language Revision of OSHA Instruction STD 3.1, Interim Fall Protection Compliance Guidelines for Residential Construction".]

[This document was edited on 12/5/2012 to strike information that no longer reflects current OSHA policy.]

With regard to whether street plates can be used as any part of a protective system in conjunction with trench boxes without a design by a registered professional engineer, please be advised that any use of street plates with pre-manufactured or job-built shields (trench boxes) must be in accordance with 29 CFR 1926.652(c)(3) or (c)(4) which requires the approval of a registered professional engineer, except when using the designs of shield systems drawn from manufacturer's tabulated data.

If we can be of any further assistance, please contact [the Directorate of Construction at (202) 693-2020.]


Roy Gurnham, P.E., Esq. Director
[Directorate of Construction]

[Corrected 2/28/2005]