Basic Hazardous Materials Terminology

Throughout the United States, there are thousands of Hazardous Materials, or HAZMAT, that are manufactured, processed, transported, handled and used every day across numerous industries and workplaces. HAZMAT includes most substances, wastes, and pollutants. There are also many U.S. regulatory agencies that mandate compliance requirements for these hazardous materials. Among them are the Occupational Safety and Health Administration (OSHA), Department of Transportation (DOT), and the Environmental Protection Agency (EPA). In this article, we will focus on OSHA-based references.


Employers whose operations work with HAZMAT in any way must be knowledgeable and comply with applicable federal, state, and local regulatory requirements. Employer compliance with the hazardous materials regulations can be a very complex undertaking with ongoing employer responsibilities in designing, developing, and implementing an effective HAZMAT program.


To those employers new to HAZMAT requirements, learning important terminology is crucial. Although there are numerous internet and mobile device app resources available for employers to define this terminology, OSHA regulations contain widely used HAZMAT terms, acronyms, and definitions.


OSHA Regulations Applicable to HAZMAT

OSHA General Industry Regulations 29CFR 1910 contains various subparts/sections applicable to HAZMAT. They include but are not limited to:

Common HAZMAT Terminologies

So, what are some of these HAZMAT terminologies? Below are just a few common ones:


Decontamination means the removal of hazardous substances from employees and their equipment to the extent necessary to preclude the occurrence of foreseeable adverse health effects.

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Hazard category means the division of criteria within each hazard class, e.g., oral acute toxicity and flammable liquids include four hazard categories. These categories compare hazard severity within a hazard class and should not be taken as a comparison of hazard categories more generally.


Hazard class means the nature of the physical or health hazards, e.g., flammable solid, carcinogen, oral acute toxicity.


Health hazard means a chemical which is classified as posing one of the following hazardous effects: acute toxicity (any route of exposure); skin corrosion or irritation; serious eye damage or eye irritation; respiratory or skin sensitization; germ cell mutagenicity; carcinogenicity; reproductive toxicity; specific target organ toxicity (single or repeated exposure); or aspiration hazard. 


Immediately dangerous to life or health (IDLH) means an atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an immediate threat to life or would interfere with an individual's ability to escape from a dangerous atmosphere.


Label means an appropriate group of written, printed or graphic information elements concerning a hazardous chemical that is affixed to, printed on, or attached to the immediate container of a hazardous chemical, or to the outside packaging.


Maximum use concentration (MUC) means the maximum atmospheric concentration of a hazardous substance from which an employee can be expected to be protected when wearing a respirator; it is determined by the assigned protection factor of the respirator or class of respirators and the exposure limit of the hazardous substance. The MUC can be determined mathematically by multiplying the assigned protection factor specified for a respirator by the required OSHA permissible exposure limit, short-term exposure limit, or ceiling limit. When no OSHA exposure limit is available for a hazardous substance, an employer must determine an MUC on the basis of relevant available information and informed professional judgment.


National Institute for Occupational Safety & Health (NIOSH) is a research agency focused on the study of worker safety and health, and empowering employers and workers to create safe and healthy workplaces. NIOSH is part of the U.S. Centers for Disease Control and Prevention (CDC), in the U.S. Department of Health and Human Services.


Permissible exposure limits (PEL) are enforceable standards promulgated by OSHA. In many cases they are derived from TLVs (see below). The PEL for a substance is the 8-hour timeweighted average or ceiling concentration above which workers may not be exposed.


Physical hazard means a chemical that is classified as posing one of the following hazardous effects: explosive; flammable (gases, aerosols, liquids, or solids); oxidizer (liquid, solid or gas); self-reactive; pyrophoric (liquid or solid); self-heating; organic peroxide; corrosive to metal; gas under pressure; or in contact with water emits flammable gas.


Recommended exposure limits (REL) are NIOSH recommended workplace concentration exposure limits for promulgation by OSHA as a Permissible Exposure Limit (PEL) but is not enforceable as is the OSHA PEL.


Safety Data Sheet (SDS) is a written or printed material concerning a hazardous chemical that is prepared in accordance with paragraph 1910.1200(g) of the Hazard Communication Standard 


Substance means chemical elements and their compounds in the natural state or obtained by any production process, including any additive necessary to preserve the stability of the product and any impurities deriving from the process used, but excluding any solvent which may be separated without affecting the stability of the substance or changing its composition.


Threshold Limit Value (TLV) can be used as a guideline for determining the appropriate level of worker protection. These values have been derived for many substances and can be found in Threshold Limit Values for Chemical Substances and Physical Agents, which is published annually by the American Conference of Governmental Industrial Hygienists (ACGIH). The ACGIH defines three categories of TLVs: Time-weighted average (TWA); Short-term exposure limit (STEL); and Ceiling (C). All three categories may be useful in selecting levels of protection at a hazardous waste site.


As previously mentioned, here are three quick reference links for DOT and EPA applications:

  1. How to Comply with Federal Hazardous Materials Regulations | FMCSA (
  2. EPA Hazard Ranking System Glossary A-L, Superfund
  3. EPA Hazard Ranking System Glossary M-Z, Superfund