3.0 Definitions

Action Level

A concentration designated in 29 CFR 1910 for a specific substance, calculated as an 8-hour time weighted average (TWA) which initiates certain required activities to ensure exposure levels are controlled.


See Select Carcinogen

Chemical Hygiene Plan

A written program developed and implemented which sets forth procedures, equipment, personal protective equipment, and work practices that are capable of protecting employees from the health hazards presented by hazardous chemicals used in the laboratory.

Designated Area

An area that may be used for work with select carcinogens, reproductive toxins or substances that have a high degree of acute toxicity. A designated area may be the entire laboratory, an area of a laboratory or a device such as a laboratory hood or glove box.


An individual employed in a laboratory workplace that may be exposed to hazardous chemicals in the course of his or her assignments.

Hazardous Chemical

A chemical for which there is statistically significant evidence, based on at least one study conducted in accordance with established scientific principles that acute or chronic health effects may occur in exposed employees.

Mixtures containing 1% of a hazardous chemical or 0.1% of a carcinogen are also defined as hazardous chemicals. The term “health hazard” includes chemicals which are carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents which act on the hematopoietic systems and agents which damage the lungs, skin, eyes or mucous membranes.


A facility where the laboratory use of hazardous chemicals occurs. It is a workplace where relatively small quantities of hazardous chemicals are used on a non- production basis. See also laboratory scale and laboratory use definitions.

Laboratory Scale

Work with substances in which the containers used for reactions, transfers, and other handling of substances are designed to be easily and safely manipulated by one person.

Laboratory Use of Hazardous Chemicals

The handling or use of such chemicals in which all of the following conditions are met:

  1. Chemical manipulations are carried out on a laboratory scale.
  2. Multiple chemical procedures or chemicals are used.
  3. The procedures involved are not part of a production process nor in any way simulate a production process, and;
  4. Protective laboratory practices and equipment are available and in common use to minimize the potential for employee exposure to hazardous chemicals.

Particularly Hazardous Substance

A term that includes select carcinogens, reproductive toxins, and substances with a high degree of acute toxicity.

Assistance with how to determine these substances is located in Appendix B, Guidance for identification of highly hazardous chemical substances.

Physical Hazard

A chemical for which there is scientifically valid evidence that it is a combustible liquid, a compressed gas, explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive) or water-reactive.

Prior Approval

Circumstances under which a particular laboratory operation, procedure or activity shall require prior approval from the employer before implementation. The intent is to ensure individuals have knowledge and procedures in place to safely perform the task.

Reproductive Toxins

Chemicals which affect reproductive capabilities including damage to chromosomes (mutagens) and effects on fetuses (teratogens).

Select Carcinogen

Any substance which meets one of the following criteria:

  1. It is regulated by OSHA as a carcinogen, or
  2. It is listed under the category “Known To Be Human Carcinogens” in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest editions), or
  3. It is listed under Group 1 (Carcinogenic To Humans) by the International Agency for Research on Cancer Monographs (IARC) (latest editions), or
  4. It is listed in either Group 2A (Probably Carcinogenic To Humans) or 2B (Possibly Carcinogenic To Humans) by IARC or under the category, “Reasonably Anticipated To Be Human Carcinogens” by NTP, and causes statistically significant tumor incidence in experimental animals in accordance with any of the following criteria:
  • After inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime, to dosages of less than 10 mg/m3.
  • After repeated skin application of less than 300 (mg/kg of body weight) per week.
  • After oral dosages of less than 50 mg/kg of body weight per day.