| The Home page of ILPI's Safety Data Sheet (SDS) Resource, the leader in SDS information since 1995! | |
| The history and philosophy behind this resource. | |
| A curated collection of books and reference materials concerning Safety Data Sheets and closely related topics. | |
| Paste your plain text SDS into the SDS-Demystifier, and it will be converted into a hypertext-enriched document with links to detailed explanations of each key term. | |
| An extensive list of frequently asked questions about Safety Data Sheets including regulations, content, compliance, and more. | |
| A humorous take on Safety Data Sheet jargon. Fill in the blanks on our entry form to generate a personalized Unsafety Data Sheet to share with your coworkers. | |
| Since 1995, we've maintained this massive curated list of the best places to find Safety Data Sheets on the Internet. | |
| Way more than a glossary, this hypertext-enhanced resource covers hundreds of SDS-related terms and expert knowledge. Each entry includes both the SDS relevance and links to additional authoritative resources. | |
| Archived results of Safety Data Sheet related polls taken by some of our millions of site visitors | |
| You are here! The OSHA regulations behind SDS regulations, including the inspection guidelines and over 400 official interpretations letters under the Hazard Communication Standard | |
| Commercial suppliers of SDS authoring and management software as well as cloud compliance services. | |
| Commercial companies that will create SDS's for your specific needs as well as SDS translation companies. |
Safety signs, banners, and scoreboards? Get yours at Safety Emporium!
OSHA Hazard Communication Letters of Interpretation
Interpretation of the Hazard Communication standard as it applies to mixtures.
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, original 1983 rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: Reaction-product principle retained; use current mixture criteria
This letter addresses the original 1983 Hazard Communication Standard (HCS), which is now obsolete. Its central principle remains useful: evaluate the actual reaction products and any unreacted ingredients. Under the current HCS, mixture classification must follow paragraph (d)(3) and the applicable criteria in Appendix A and Appendix B, rather than the letter's simplified testing-or-components approach.
The local text and OSHA's online original both print “10 percent completion.” That wording is preserved below; it should not be read as a current general conversion threshold. Identify the mixture's actual composition and hazards. Current paragraph (d)(2) does not require new testing; use the available evidence and applicable mixture criteria.
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.
January 29, 1986
Safety Emporium has all kinds of lab equipment such as stirring hot plates.
Michael J. Reale, Ph.D.
Director of Regulatory Affairs
GLYCO, Inc.
Post Office Box 5100
Norwalk, Connecticut 06856-5100
Dear Dr. Reale:
This letter is in response to your October 24, 1985, request for an interpretation regarding the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard as it pertains to mixtures. Please accept my apology for the delay in responding. The overwhelming number of letters and telephone calls regarding the Hazard Communication has caused unavoidable delays in responding to the public's concerns.
In the example given in your letter, chemicals C and D, formed by chemical reaction of A and B, would be treated as new chemical entities for the purposes of hazard determination. You would then be required to evaluate the hazards of chemicals C and D. In cases where reaction does not proceed to 10 percent completion, the resulting chemicals would be treated as a mixture of chemicals C, D, and unreacted A and B. A hazard determination must then be accomplished be testing the mixture as a whole, or by assuming that the mixture contains components C, D, A and B.
[ILPI note: OSHA's original also prints “10 percent completion.” It is preserved here, not adopted as a current conversion threshold. Use actual composition, current mixture classification, and available evidence; new testing is not required.]
Again, we regret any inconvenience caused by this delay. If you have further questions on this matter, please feel free to contact OSHA's Office of Health Compliance Assistance at 200 Constitution Avenue, N. W., Room N-3606, Washington, D. C. 20210 or telephone (202) 523-8036.
Sincerely,
John B. Miles, Jr., 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/1986-01-29.