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OSHA Hazard Communication Letters of Interpretation
Hazard determination criteria for corrosive liquids.
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, 1987 expanded rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: Evidence-based evaluation retained; apply modern corrosion/irritation criteria
This letter addresses the HCS as expanded in 1987, an obsolete version of the Hazard Communication Standard (HCS). Its advice to evaluate relevant evidence and distinguish corrosion from irritation remains useful. The historical floor lists, appendix functions, and freely selected “appropriate hazard warning” approach are superseded by current classification and label criteria.
Under the current HCS, use hazard classification and skin corrosion/irritation/serious eye damage/irritation criteria, including their pH provisions. Extreme pH can be important evidence; do not read the historical answer as permission to ignore it. The standard does not require new testing, but available evidence must be evaluated under the applicable rules.
Apply shipped-container label elements and Appendix C and SDS requirements; “Caution” is not one of the current HCS signal words. The letter's titanium tetrachloride example is incorrect at ordinary room temperature: it is a liquid, as noted below. This does not alter the need to evaluate corrosivity in either solids or liquids.
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This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter.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.
December 1, 1988
Mr. John Thomas Cooney
Plant Chemist
SUS Chemical Company, Inc.
Post Office Box 10027
Rock Hill, South Carolina 29731
Dear Mr. Cooney:
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This is in response to your letter of September 7, regarding the hazard determination requirements under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard 29 CFR 1910.1200. Please accept by apology for the delay in response.
Our responses to your questions are numbered in the sequence in which they were posed.
Question 1: If a company chooses not to have their products tested by this method (as stated by 29 CFR 1910.1200), what criteria would determine if a product is classified as corrosive on hazard warning labels and MSDS sheets?
Answer: As a chemical manufacturer, importer or employer evaluating chemicals, you are not required to follow any specific test methods stated in 29 CFR 1910.1200 for the hazard determination. You must, however, be able to demonstrate that the hazards of the chemicals produced or imported have been adequately ascertained in accordance with the criteria set forth in Appendix B, Hazard Determination found in 29 CFR 1910.1200. In making the hazard determination you are not required to perform chemical testing. The evaluation is to be based on currently available information. You are required to consider all available scientific evidence concerning the hazard of a chemical in addition to consulting the floor reference sources, listed in paragraph (d)(3) of the standard. These are 29 CFR Part 1910, Subpart Z, Toxic and Hazardous Substances, OSHA; and Threshold Limit Values for Chemical Substances and Physical Agents in the Work Environment, ACGIH. Additional information sources to evaluate the hazards associated with the chemicals are listed in Appendix C to 29 CFR 1910.1200.
[ILPI note: The original Appendix B concerned hazard determination and Appendix C listed information sources. Their present functions differ: current Appendix A addresses health criteria, B physical criteria, and C label elements. Apply current classification.]
Question 2: Would pH measurements define corrosivity of that product or would there be other test methods?
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Answer: The pH is a measure of the acidity or alkalinity of a solution. Although pH is a characteristic of a corrosive liquid, it would not define corrosivity, as a corrosive material can be liquid or solid. Titanium tetrachloride is an example of a solid corrosive material To make a thorough and defensible hazard determination, not only pH but all relevant data available must be examined.
[ILPI note: The titanium tetrachloride example is incorrect at ordinary room temperature: TiCl4 is a liquid. Tungsten hexachloride (WCl6) is a solid example.]
[ILPI note: At issuance: 1910.1200, 1987 expanded rule (PDF). Current counterparts: skin corrosion/irritation and serious eye damage/irritation. Their pH criteria and other relevant evidence govern; extreme pH must not simply be disregarded. The existing ILPI correction of the physical-state example is retained.]
Question 3: Should other labels such as "CAUTION IRRITANT" be used in place of "CORROSIVE?"
Answer: An irritant is a chemical, which is not corrosive, but which causes a reversible inflammatory effect on living tissue by chemical action at the site of contact. If the evidence available on a chemical indicates it is an irritant hazard rather than corrosive, the appropriate hazard warning must be used. The hazard warning must convey the hazard of the chemical and the target organ effects, when such information is available (i.e., eye irritant or skin irritant).
[ILPI note: Apply current skin/eye criteria and label elements. Current HCS signal words are “Danger” and “Warning”; the proposed “Caution” wording below is historical.]
We hope this information is helpful to you. If we can be of further assistance to you, please contact us again.
Sincerely,
Directorate of Compliance Programs
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1988-12-01.