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.

September 20, 1994

J.B. Saunders
Maryland Rail Car
P.O. Box 10
Elk Mills, Maryland 21920

Dear Mr. Saunders:

This letter is in response to your telephone conversation with directorate staff and a facsimile of an interpretation letter by the Dallas Regional Office to Mr. J.R. Silver of Silver Inspection Services. Please accept our apology for the delay in this response.

The reclassification of a permit space as a "non-permit space," whether it is a "tank container" or any other Permit-required Confined Space (PRCS), must be accomplished in accordance with 29 CFR 1910.146(c)(7). This paragraph states that the space to be reclassified must pose no actual or potential atmospheric hazards and all other hazards within the space must be eliminated.

The interpretation letter written by Region VI, addressing the reclassification of Silver Inspection Services' tank containers through the application of Paragraph (c)(7), is very narrow in its application. This letter responds to a specific condition. It may not be applicable to the referenced tank containers if any condition is present or arises which would allow any portion of the space to contain a potentially hazardous atmosphere. In OSHA's experience, "removal" of material/"cleaning" of tanks of this type generally do not result in a non-permit spaces because the residues persist and pose a potential atmospheric hazard.

Examples of conditions which would render paragraph (c)(7) inoperative are: oxidation of the tank shell; leaching of the former contents or by-products absorbed by the tank coating or lining into the permit space; or leaking of the contents trapped between the lining and the tank shell by a defective tank coating or lining. Some other conditions which could affect these examples and thus increase the potential for an atmospheric hazard are: rising or falling outside temperature; changing or stratified tank shell temperature from exposure to sunlight or other sources of radiant energy; and barometric fluctuations.

A major consideration for determining the appropriateness of paragraph (c)(7) is whether there is potential for a hazardous atmosphere to develop. If mechanical ventilation is required to maintain acceptable conditions, then (c)(7) cannot be employed because the hazard is being controlled, not eliminated.

Should you have further questions on this subject please contact Mr. Don Kallstrom in the Office of General Industry Compliance Assistance (202) 219-8031.


John B. Miles, Jr., Director
Directorate of Compliance Programs