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Ventilation at powered-truck battery charging

Summary An industrial supplier asked what adequate ventilation meant for powered-truck battery charging. OSHA said natural or mechanical ventilation had to keep hydrogen below its 4.1% lower explosive limit at the charging site. An ordinary exhaust fan could suffice if it achieved that result.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1976-01-26
Date issued
January 26, 1976
Status
Active
Status last verified October 10, 2026
Topics
Workplace Safety OSHA 1910 Ventilation Battery Charging
Source
View the official document

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About this page: The full text below is the official document from Occupational Safety and Health Administration (OSHA). Ezel adds the plain-English summary and tracks the document's status. The official source linked on this page is authoritative for any reliance.

January 26, 1976

Mr. John R. Reilly
Corporate Safety Director
Corporate Headquarters
Fisher Scientific Company
[Recipient address omitted]
Dear Mr. Reilly:

Your letter of January 16, 1976 requested definition of the phrase "Adequate ventilation" as used in 29 CFR 1910.178(g)(2). The source of this standard is National Fire Protection Association No. 505 - 1969: Powered Industrial Trucks, Section 700--Changing and Charging Storage Batteries.

"Adequate ventilation" as used in the indicated standard means providing natural, mechanical--general, or mechanical dilution ventilation sufficient to limit the accumulation of hydrogen gas in air at the charging site to levels below the lower explosive limit (4.1%).

A "typical exhaust fan" could meet this requirement if it were used in a manner such that the concentrations of the hydrogen gas in the fan's ambient air never exceeded the lower explosive limit.

Thank you for your interest in a safe workplace.

Sincerely yours,
DAVID H. RHONE
Regional Administrator

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