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OSHA Hazard Communication Letters of Interpretation
Guidance on whether an inert gas in the non-compressed state represent hazardous chemicals under the Hazard Communication Standard.
- Issued
- Record type
- Interpretation
- Historical standard
- HCS 1994, pre-GHS archive
- Current standard
- HCS 2024, as amended
ILPI assessment: Simple-asphyxiant coverage remains; current classification is explicit
This letter addresses the obsolete 1994 version of the Hazard Communication Standard (HCS). Its main HazCom conclusion remains consistent: atmospheric-pressure gas can be hazardous by displacing oxygen, even when it is chemically inert and not compressed.
Under the current HCS, simple asphyxiants are explicitly included in hazardous-chemical coverage. Evaluate actual releases, foreseeable emergencies and applicable labels/SDSs rather than treating the old acute-health/toxicity wording as the current classification scheme. Asphyxiant explains oxygen displacement; chemical inertness does not imply safety. Separate confined-space and respiratory-protection requirements may apply. No oxygen-deficient task is authorized here.
OSHA marks its matching original corrected 12/6/2024.
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This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter.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 25, 1995
Richard F. Andree, CSP, PE, Ph.D.
Vice President - Director of Safety and Health Services
Lovell Safety Management Company, Inc.
161 William Street
New York, New York 10038-2675
Dear Mr. Andree:
This is in further response to your letter of April 11, to the Occupational Safety and Health Administration (OSHA), requesting guidance on whether an inert gas in the non-compressed state represent hazardous chemicals under the Hazard Communication Standard (HCS), 29 CFR 1910.1200 [ILPI: Original HCS 1994 context · Current HCS]. Your letter specifically inquired about gases such as argon, nitrogen and helium at atmospheric pressure. Please accept my apology in the delay in this response.
OSHA agrees with your statement that inert gases are classified as a simple asphyxiants. Patty's Industrial Hygiene and Toxicology defines a simple asphyxiant as: "physiologically inert gases that can act principally by dilution of the atmospheric oxygen below partial pressure necessary to maintain an oxygen saturation in the blood sufficient for normal tissue respiration."
Inert gases, such as argon, nitrogen and helium, have the potential to create a hazardous atmosphere (less than 19.5% oxygen) and, where that potential exists, are considered by OSHA as hazardous chemicals presenting an acute health hazard and covered by the standard. The HCS would not apply where employees are not occupationally exposed, under normal conditions of use or in a reasonably foreseeable emergency, to the oxygen displacing hazard associated with inert gases. Obviously, argon, nitrogen and helium occur naturally in the atmosphere, and under those conditions they are not hazardous chemicals.
The HCS requires chemical manufacturers, or importers to assess the hazards of chemicals which they produce or import, and all employers to provide information to their employees about the hazardous chemicals to which they are exposed, by means of a hazard communication program, labels and other forms of warning, material data safety sheets (MSDSs), and information and training. Included in the HCS is paragraph (c) [ILPI: Original HCS 1994 context · Current HCS] which contains a broad definition of the term "health hazard." Appendix A of the HCS [ILPI: Original HCS 1994 context · Current HCS; modern simple-asphyxiant coverage is explicit] also provides further definition and explanations of the scope of health hazards including acute health hazards. Enclosed for your reference is a copy of a February 9, Hazard Communication; Final Rule which contains a number of minor changes and technical amendments to clarify further the regulatory requirements.
[ILPI note: At issuance: HCS 1994, pre-GHS archive. The modern HCS explicitly defines simple asphyxiants and includes them as hazardous chemicals. The old Appendix A/acute-health shorthand is not the current classification route for oxygen displacement.]
You objected to the language in the March 4, 1993, letter to Matthew McFarland stating that toxicity has been established in inert gases, and that the manufacturer, importer, and/or distributor has the duty of performing a complete hazard determination. To elaborate on the underlined phrase we mean the toxic effects of excessive levels of inert bases has been well established. Hopefully, this clarifies the language and addresses your concern.
We hope this information provides you with the necessary guidance. Thank you for your interest in worker safety and health. Should you require additional information please contact the Office of Health Compliance Assistance at (202) 219-8036.
Sincerely,
Joseph A. Dear
Assistant Secretary
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1995-01-25.