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OSHA Hazard Communication Letters of Interpretation
MSDS requirements for complex mixtures with similar hazards.
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, original 1983 rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: Generally consistent with the current HCS
This letter addresses the original 1983 Hazard Communication Standard (HCS), which is now obsolete. Its central conclusion appears consistent with current paragraph (g)(4): one SDS may cover complex mixtures with similar hazards and contents when their chemical ingredients are essentially the same but their specific composition varies. The letter's acceptance of a small range of flash points or vapor pressures is conditional on the hazard potential remaining the same; it is not permission to combine materially different hazards on one SDS.
Under the current HCS, apply the hazard classification requirements and current criteria, including Appendix B.6 for flammable liquids. The letter's contrast between “flammable” and “combustible” reflects the old HCS terminology; it should not replace the current hazard categories. A shared SDS must still meet current format and content requirements, including Section 9 physical and chemical properties.
Last reviewed: .
About this ILPI assessment
This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter. This assessment reflects editorial judgment informed by human review and AI assistance. It is an opinion, may contain errors or omissions, and is not an official OSHA determination. For guidance on how OSHA requirements apply to your circumstances, contact your local OSHA office.
OSHA's notice about interpretation letters
The following notice is published on OSHA's interpretation pages; it is general guidance, not a letter-specific withdrawal notice.
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.
Source: OSHA's original letter page.
July 9, 1985
Mr. D. R. Roeing
Government Affairs Manager
Croda Inks Corporation
7777 North Merrimac Avenue
Niles, Illinois 60648-3490
Dear Mr. Roeing:
Thank you for your letter of April 26 regarding the Hazard Communication Standard (HCS). [ILPI note: At issuance: original 1983 rule (PDF). Current counterpart: paragraph (g)(4), similar mixtures.] I apologize for our delay in responding.
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As you noted, the HCS allows manufacturers of complex mixtures with similar hazards and contents to prepare only one material safety data sheet for these mixtures. [ILPI note: This provision continues in current paragraph (g)(4); use the current SDS format.] In your letter, you state that these mixtures have varying flash points and vapor pressures, and ask whether it is necessary to list these for the mixture. If the variation is slight, that is, the flash points and vapor pressures are within a small range and the hazard potential is the same, reporting of the range would suffice. However, if the hazard potential changes (e.g., a different flashpoint results in a chemical being flammable rather than combustible), then the specific information must be reported. [ILPI note: The flammable/combustible distinction above uses historical HCS terminology. Current Appendix B.6 uses flammable-liquid categories; assess each mixture under the current criteria.] The key to determining the appropriateness is to ensure similarity in contents and hazard--without both, a single data sheet will not suffice.
We hope this information will be helpful to you. If we can be of further assistance, please do not hesitate to contact us.
Sincerely,
Director
Directorate of Field Operations
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1985-07-09.