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.

March 12, 1996

Mr. Barron L. Stroud, Jr.
Law Offices of Miles
& Stockbridge
10 Light Street
Baltimore, MD 21202-1487

Dear Mr. Stroud:

This is in response to your April 18 letter requesting clarification regarding the grounding requirements of 29 CFR 1910.304 with respect to a battery charger used with rechargeable power tools. Please accept our apology for the delay in responding. Your question and our reply follow.

Question: Is an approved battery charger required to be either grounded or double-insulated under the requirement of 29 CFR 1910.304?

Reply: Paragraph 1910.304(f)(5)(v) contains requirements for grounding cord- and plug-connected equipment. According to this rule, a cord- and plug-connected battery charger must be grounded or double-insulated:

1. If it is used in a hazardous location, defined under paragraph 1910.307.


2. If it operates at more than 150 volts, or

3. If it is used in damp or wet locations or by employees standing on the ground or on metal floors or working inside of metal tanks or boilers.

If a system of double insulation is used, the portable battery charger must be distinctively marked to indicate that it utilizes an approved system of double insulation. (See the paragraph following 29 CFR 1910.304(f)(5)(v)(c)(8)).

Please note under paragraph 1910.399 that "approved" is defined as "acceptable" which is defined as "accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory" (NRTL). An employer must follow the conditions of use assigned to approved equipment or installations by the NRTL to be in compliance with Occupational Safety and Health Administration regulations. A listing of NRTL's is enclosed for your use.

If we may be of further assistance, please contact the Office of General Industry Compliance Assistance, M. Ronald Davies, telephone (202)219-8031, extension 110.


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


April 28, 1995

Ronald Davies
Safety Engineer
United States
Department of Labor
200 Constitution Avenue N.W.
Room 3107
Washington, D.C. 20210

Re: Request For Clarification

Dear Mr. Davies:

Thank you for your assistance in responding to my recent inquiry. I contacted you to seek clarification regarding the application of certain provisions of the federal labor code with respect to a battery charger used with rechargeable power tools.

My specific question was whether a laboratory approved battery charger was required to be either grounded or double-insulated under the portions of the Code of Federal Regulations pertaining to electrical equipment, with particular reference to 29 C.F.R. 1910.304. You advised that the charger, when used in accordance with the conditions of its U.L. approval, satisfied OSHA's regulatory requirements and was not required, in addition, to be grounded or double-insulated. You also indicated that a written request was required for the issuance of a formal opinion by OSHA.

Please accept this letter as a formal request for clarification on the question stated above.

Once again, thank you for your cooperation and assistance.

Very truly yours,

Barron L. Stroud, Jr