- Standard Number:
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.
February 13, 1981
MEMORANDUM FOR: ROGER CLARK
Regional Administrator
THRU: JOHN B. MILES, JR.
Director
Office of Field Coordination
FROM: BRUCE HILLENBRAND
Acting Director
Federal Compliance and State Programs
SUBJECT: November 4, 1980, Memorandum Requesting an
Interpretation of 29 CFR 1910.1017(b)(5) and
the Definition of "Massive Release" of Vinyl
Chloride
The term "massive release" applies to a concentration of 100 ppm or higher of vinyl chloride in the general work area, or the general workroom air. It refers to an unexpected or uncontrolled release of vinyl chloride; i.e., leakage due to equipment failure such as from a relief valve, pipe leak or process (unit) leak which is considered an emergency.
November 4, 1980
SUBJECT: Interpretation of 1910.1017(b)(5). Definition of
"Emergency".
TO: JOHN B. MILES, JR.
Director, Office of Field Coordination
A more detailed explanation of the term "massive release" in the subject definition is required. CPL 2-2.4 indicates that an unexpected release of vinyl chloride is "massive" where the concentration of VC is greater than 100 ppm. Was this explanation intended to refer to concentrations of VC in the general workroom air or in the worker's breathing zone? Or did it include a location directly at the point of a leak where the VC level would undoubtedly exceed 100 ppm? If the latter was meant, it would then be incumbent on employers to report to OSHA practically any unexpected release of this substance from a piping system, vessel, etc.
We would appreciate your comments in this regard.
Roger A. Clark
Regional Administrator