Ezel / Labor Guidance / US
Back to Federal guidance

Flammable-liquid rule for trowel mastic

Summary A construction company asked whether a named trowel mastic fell under OSHA's flammable-liquid construction rule. OSHA said the general-industry definition of 'liquid' should be used and that the mastic would be exempt if its penetration was in the stated 70-to-90 range. OSHA archives the letter.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1977-09-06
Date issued
September 6, 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OSHA labels this an archive document and warns that it may no longer represent OSHA policy.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 Flammable Liquids Construction Materials
Source
View the official document

Apply this to your situation

This page explains the general guidance. Ask about your specific situation and see what current federal labor law says, with citations.

The current status of this document is unclear
OSHA labels this an archive document and warns that it may no longer represent OSHA policy.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 Treat this page as historical context, not current guidance, and verify current law before relying on anything here.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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.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 6, 1977
Mr. William F. Black
Vice President
J.W. Bateson Company, Inc.
[Recipient address omitted]
Dear Mr. Black:
This is in response to your letter dated March 23, 1977, and confirms a recent telephone conversation with a member of my staff. Your letter concerned 29 CFR 1926.152 as it applies to Flintkote Trowel Mastic 710-23.
Subpart F of 29 CFR 1926 does not contain a definition of "liquid", therefore, in following 29 CFR 1910.5 and Chapter VIII of the Field Operations Manual you should go to 29 CFR 1910.106(a)(17) which defines "liquid" as:

...any material which has a fluidity greater than that of 300 penetration asphalt when tested in accordance with ASTM Test for Penetration for Bituminous Materials, D-5-65.

The definition would exempt Flintkote Trowel Mastic 710-23 from coverage by 29 CFR 1926.152 if the penetration of this material is in the 70 to 90 range.
If I can be of any further assistance, please feel free to contact me.
Sincerely,
Richard P. Wilson
Deputy Director
Federal Compliance and State Programs

Related guidance

Permanently labeled locks for electrical lockout Opinion Letter · August 17, 2026 Helmet selection for lateral head-impact hazards Opinion Letter · August 17, 2026 Asbestos precautions when restoring drywall after flood damage Opinion Letter · May 7, 2026 Enforcement policy for recording and reporting COVID-19 cases Guidance · March 31, 2026

What does federal law require in your situation?

Ezel checks current federal labor law against your facts and answers with citations.

Opens in Ezel Pro.

  • Checks the law as it stands today, not only this page
  • Cites every source it relies on, so you can verify it
  • Chat, drafting and research in one workspace