Standard Interpretations - Table of Contents
• Standard Number: 1926.302(b)(4); 1926.405(a)(2); 1926.405(a)(2)(ii)(B)

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

October 4, 2000

Joy C. DesRosier, ASP COHN-SM
Senior Safety Consultant
Argonaut Insurance Company
Financial Plaza, Suite 850
6900 College Boulevard
Overland Park, Kansas 66211

Re: Interpretations of 29 CFR 1926.302(b)(4) and 1926.405(a)(2)

Dear Ms. DesRosier:

Thank you for your letter of October 12, 1999, in which you requested clarification of OSHA standards that regulate use of compressed air for cleaning and electrical installations and equipment. We apologize for the delay in providing this response.

Using compressed air to clean concrete form and mill scale

Questions: Section 1926.302(b)(4) provides that "compressed air shall not be used for cleaning purposes except where reduced to less than 30 p.s.i. and then only with effective chip guarding and personal protective equipment which meets the requirements of subpart E of this part. The 30 p.s.i. requirement does not apply for concrete form, mill scale and similar cleaning purposes." What is the rationale for that exception? What are some examples of what would constitute "similar cleaning purposes?"

Answer: This OSHA standard began as a standard under the Construction Safety Act (CSA), prior to the enactment of the Occupational Safety and Health Act. At first, the CSA standard did not have the exception. The exception was added in response to a comment made during rulemaking under the CSA. The amended CSA standard was then adopted as an OSHA standard under section 6(a) of the OSH Act.

Section 6(a) directed the Labor Department to adopt established federal standards as OSH Act standards. It further called for, in the event of a conflict between any such standards, adoption of the most protective standard. A comparable standard existed under the Walsh Healy Act, which was also adopted as an OSHA standard pursuant to Section 6(a). However, that standard does not contain the exception. In view of this background, OSHA will construe the exception narrowly. The primary consideration is not whether a higher pressure would make cleaning quicker or easier, but whether the higher pressure is necessary to remove a tightly adhering residue. If you have a particular material in mind and want to know if it would be included in the exception, we would be happy to provide guidance on that question.

Importantly, the standard requires chip guarding and personal protective equipment to be used whenever compressed air is employed for cleaning purposes. Effective chip guarding means any method or equipment which will prevent a chip or particle (of whatever size) from being blown into the eyes or skin of the operator or other workers in the area.

Temporary electrical wiring on construction sites

Your second inquiry concerns the propriety of using temporary panels for multiple GFCI outlets wired with unprotected, Romex-style electrical cable, running across floors and up the outside of walls to other floors (Romex is a trade name. The electrical classification for this type of electrical cable is nonmetallic-sheathed cable). Your understanding is that §1926.405 prohibits such temporary electrical cable installations, although you note that some qualified electricians differ with your position. You ask the following two questions concerning such installations:

Question 3: Do these wiring configurations meet the standard?

Answer: Section 1926.405(a)(2)(ii)(B) permits Romex-style electrical cable (nonmetallic-sheathed cable-type NM) to be used as temporary wiring which may be of a class less than would be required for a permanent installation. Temporary wiring of nonmetallic-sheathed cable shall be secured by staples, cable ties, straps or similar fittings designed and installed so as not to da