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Employee withdrawal after flammable gas in tunnels

Summary An OSHA region asked what 'shall be withdrawn' meant for flammable gas detected in an underground workplace. OSHA said employees must leave the tunnel and portal area at 1.5 percent or higher, and power in the endangered area must remain off until gas falls to 1 percent or less. OSHA archives the memo.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1977-09-28
Date issued
September 28, 1977
Status
Archived by the agency
OSHA labels this an archive document and warns that it may no longer represent OSHA policy.
Status last verified October 10, 2026
Topics
Workplace Safety OSHA 1926 Underground Construction Flammable Gas Evacuation
Source
View the official document

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OSHA labels this an archive document and warns that it may no longer represent OSHA policy. It may no longer reflect the agency's current position. Treat this page as historical context, not current guidance, and verify current law before relying on anything here.
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.

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

September 28, 1977

MEMORANDUM FOR: JACK D. TORREY
Acting Regional Administrator Region VIII

THRU: DONALD E. MACKENZIE
Field Coordinator

FROM: RICHARD P. WILSON
Deputy Director, Federal Compliance and State Programs

SUBJECT: Interpretation of 29 CFR 1926.800(c)(2)(vi) line 5 "shall be withdrawn".

If 1.5 percent or higher concentration of flammable gas is detected in air returning from an underground working place, the employees shall be withdrawn from the tunnel and away from the portal. The power shall be cut off to the portion of the area endangered by such flammable gas until the concentration of such gas is reduced to 1 percent or less.

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