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.

November 8, 1991

Mr. Joseph Green
Occupational Health and Hygiene
Corporation of America
Suite 20
2777 Finley Road
Downers Grove, Illinois 60515

Dear Mr. Green:

This is in further response to your letter of September 25, to the Occupational Safety and Health Administration (OSHA). Your letter requested an interpretation of the Hazardous Waste Operations Emergency Response standard (29 CFR 1910.120).

It is not the intent of the Agency to define an emergency condition in terms of an arbitrary quantity of material released due to the diversity of workplace conditions, conditions of chemical use, and types of chemicals used.

When, as a consequence of a release of a hazardous substance the following conditions, or similar conditions, may develop, such situations would normally be considered emergency situations requiring an emergency response effort:

  1. High concentrations of toxic substances.
  2. Situation that is life or injury threatening.
  3. Imminent Danger to Life and Health (IDLH) environments.
  4. Situation that presents an oxygen deficient atmosphere.
  5. Condition that poses a fire or explosion hazard.
  6. Situation that required an evacuation of the area.
  7. A situation that requires immediate attention because of the danger posed to employees in the area.

Incidental releases that can be handled safely by employees in the immediate area, without the aid of a coordinated response effort from employees outside the area, would not be considered an emergency incident under 29 CFR 1910.120.

Employers, who intend to evacuate employees from the danger zone when an emergency situation occurs and who do not expect employees to assist in handling the emergency, are exempt from developing an emergency response plan provided an emergency action plan is developed in accordance with 29 CFR 1910.38(a).

The intent of the standard is to protect employees from exposure to the health and physical hazards of hazardous substances associated with hazardous waste operations and emergency response activities. Absent testing data on the mixture as a whole, the hazards of a mixture containing hazardous substances would be expected to be treated as a hazardous substance for compliance purposes.

The determination of how much of a solvent mixture spill (containing 10-100 ppm of benzene) would represent an emergency, is dependent upon many factors. It is not possible to respond to your specific question based on the information provided. However, in general, a theoretical concentration for each component part can be calculated based on the quantity of solvent spilled, the percentage by weight of volume of each component, and the size of the spill area. In the event the components of a mixture pose an additive effect, the TLV for the mixture can be calculated. Dependent upon the quantity of a solvent expected to be released and the size of the spill area, a determination could then be made as to whether or not such a concentration would result.

When the concentration of the mixture as a whole or the concentration of the component parts poses a condition previously described, an emergency situation would be anticipated requiring an emergency response.

If you have any further questions please contact us at [(202) 693-2190].


Gerard F. Scannell
Assistant Secretary

September 25, 1991

Mr. Gerard F. Scannell
Assistant Secretary for Occupational Safety and Health
U.S. Department of Labor
200 Constitution Avenue, N.W.
Washington, DC 20210

Dear Mr. Scannell:

The purpose of this letter is to request an interpretation of the requirements in OSHA's regulations 29 CFR 1910.120 Hazardous Waste Operations and Emergency Response.

With regard to the definitions in these regulations, the term "hazardous substance" is defined as follows:

"Hazardous substance" means any substance designated or listed under paragraphs (A) through (D) of this definition, exposure to which results or may result in adverse affects on the health or safety of employees:

(A) Any substance defined under section 101(14) of CERCLA;
(B) Any biological agent and other disease-causing agent which after release into the environment and upon exposure, ingestion, inhalation, or assimilation into any person, either directly from the environment or indirectly by ingestion through food chains, will or may reasonably be anticipated to cause death, disease, behavioral abnormalities, cancer, genetic mutation, physiological malfunctions (including malfunctions in reproduction) or physical deformations in such persons or their offspring;
(C) Any substance listed by the U.S. Department of Transportation as hazardous materials under 49 CFR 172.101 and appendices; and
(D) Hazardous waste as herein defined.

Further, the term "emergency response" is defined as follows:

"Emergency response" or "responding to emergencies" means a response effort by employees from outside the immediate release area or by other designated responders - (i.e., mutual-aid groups, local fire departments, etc.) to an occurrence which results, or is likely to result in an uncontrolled release of a hazardous substance. Responses to incidental releases of hazardous substances where the substance can be absorbed, neutralized, or otherwise controlled at the time of release by employees in the immediate release area, or by maintenance personnel are not considered to be emergency responses within the scope of this standard. Responses to releases of hazardous substances where there is no potential safety or health hazard (i.e., fire, explosion, or chemical exposure) are not considered to be emergency responses.

We are currently working with several private sector industrial clients to assist them in implementing their "Hazardous Substance Emergency Response Plans." The following questions have been raised:

  1. Excluding "incidental releases" as described by OSHA in the definition of Emergency Response, are there any criteria on the quantity or amount of a hazardous substance that has to be involved in a release for that incident to be considered as requiring an Emergency Response?

    As an example, for the hazardous substances defined under section 101(14) of CERCLA, would an employer be required to be prepared for an Emergency Response if a release involved only "reportable quantities" of the hazardous substance?

    Or, is the employer required to be prepared for an Emergency Response for any release, excluding "incidental releases," of a hazardous substance which results or may result in adverse affects on the health or safety of employees?

  3. How does the definition of "hazardous substance" apply to mixtures?

    As an example, a solvent blend has as a minor component (e.g. 10-100 ppm) a chemical (e.g., benzene) which appears on the designated lists of hazardous substances. How much solvent blend would have to be involved for the release to be considered as requiring an Emergency Response?

    This type of situation could occur for numerous chemicals, including those used as protective coatings and for water treatment.

We would appreciate your review of these questions and a written reply stating how OSHA interprets the requirements of 29 CFR 1910.120.

Your prompt response will be appreciated. Please feel free to contact me should you need to discuss our inquiry.

Very truly yours,

Joseph D. Green, CIH, CSP
Industrial Hygiene Division

[Corrected 1/6/03]