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 http://www.osha.gov.

March 24, 1977

Mr. Michael F. Dolan
Industrial Hygienist
Vulcan Materials Company
P.O. Box 545
Wichita, Kansas 67201

Dear Mr. Dolan:

This is in response to your letter of October 4, 1976, in which you requested clarification of several parts of 29 CFR 1910.1017, the Vinyl Chloride Standard.

"Massive release" of vinyl chloride as used in 1910.1017(b)(5) to define "emergency" means a physically imposing and impressive gaseous release irrespective of considerations of toxicity. Typical concentrations associated with a massive release of vinyl chloride cannot be pinned down because of the diverse nature of the surroundings in which they may occur. Massive release of vinyl chloride is recognized by the event of gaseous vinyl chloride escaping under positive pressure with concomitant liquid vinyl chloride spray generation, and/or cloud formation, and/or ice clump formation at the point of escape.

A massive release of vinyl chloride is regarded as an emergency because it creates a potential for fire and/or explosion, and/or for acute toxication of employees, and/or for predisposing employees to future development of disease such as cancer.

In order to clarify the term "hazardous release" used in 1910.1017(i)(1), the clause it is used in must be explained. The clause establishes one of the provisions that must be included in a written operational plan for emergency situations. Specifically, the plan must require employees used to combat emergencies or to correct existing massive releases of vinyl chloride to be equipped in accordance with paragraph 1910.1017(h). More precise terminology might have been used in 1910.1017(i)(1), i.e., "emergencies" instead "hazardous operations" and "massive releases" instead of "hazardous releases."

The protective equipment required for employees engaged in hazardous operations needs to be worn during the release of vinyl chloride, during the period that the air in their work space remains contaminated with vinyl chloride, and during periods where there is a potential for the release of vinyl chloride to suddenly and unpredictably occur.

I hope you find the information provided helpful.


Richard P. Wilson,
Deputy Director Federal
Compliance and State Programs