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• Standard Number: 1910.147

August 28, 1995

William K. Principe
Constangy, Brooks & Smith
Suite 2400
230 Peachtree Street, N.W.
Atlanta, Georgia 30303-1557

Dear Mr. Principe:

This letter is in response to the questions in your letter of January 3, 1995. The questions and responses are as follows:

Q 1. Is compliance with the Lockout/Tagout Standard 29 CFR 1910.147, sufficient to demonstrate that possible energization is no longer a hazard and that, as a consequence, a permit-required confined space can be classified as a non-permit required confined space?

R. A permit-required confined space can be reclassified as a non-permit required confined space if it does not contain any actual or potential hazardous atmosphere and all hazards within the space are eliminated. For the purpose of reclassifying a permit-required confined space, which has potential energy sources in it, the methods which must be utilized are dependent upon what types of energies must be eliminated.

Compliance with OSHA's Lockout Tagout Standard is considered to eliminate electro-mechanical hazards. However compliance with the requirements of the Lockout/Tagout Standard is not considered to eliminate hazards created by flowable materials such as steam, natural gas, and other substances that can cause hazardous atmospheres or engulfment hazards in a confined space. In a permit-required confined space these types of hazards will be considered eliminated only by the use of the techniques described in the definition of the term "isolation". The definition of the term "isolation" is in paragraph (b) of 29 CFR 1910.146. The techniques listed in the definition are blanking, blinding, misaligning or removing sections of lines or pipes and a double block and bleed system.

Q 2. Does the implementation of an appropriate lockout procedure which blocks out a potentially hazardous atmosphere, allow an employer to treat a confined space as not having a potential for an atmospheric hazard?

R. No. As indicated in the response to the first question flowable materials, which can cause either a hazardous atmosphere or an engulfment hazard, can only be eliminated by the use of the techniques described in the definition of the term "isolation". Continuous ventilation used to insure that a hazardous atmosphere is not created is considered to be a control method rather than elimination of the atmospheric hazard. It is important that the distinction between elimination and control be understood.

Q 3. For permit-required confined spaces that have been reclassified as non-permit required confined spaces, can continuous monitoring be used to ensure that atmospheric hazards remain eliminated?

R. Such a procedure should not be necessary if the atmospheric hazard is eliminated. In order for a permit-required confined space, with an actual or potential atmospheric hazard, to be reclassified as a non-permit required confined space the atmospheric hazard must be eliminated.

Q 4. Under paragraphs (c)(5)(i) and (c)(5)(ii) of 29 CFR 1910.146 can continuous monitoring be used in lieu of continuous forced air ventilation if no hazardous atmospheric is detected?

R. No. The entire basis for the permitting the alternate entry procedures, described in paragraph (c)(5) of 29 CFR 1910.146, is that any actual or potential hazardous atmosphere will be controlled by continuous ventilation. This is of particular significance since among other things the alternative procedures do not require the presence of an attendant during entry operations. Entrants could be severely injured or killed if a hazardous atmosphere does develop and there will be no one available to aid them in getting out of the space.

In addition to the preceding questions there were several issues raised in the examples in your letter relative to three different permit-required confined spaces. Those issues are addressed in the following paragraphs.

Two different procedures must be implemented in order to reclassify the tank, described in example "a" of your question 4, as a non-permit required confined space. The hazard associated with the agitator will be considered to be eliminated if the requirements of the Lockout/Tagout Standard are followed. The hazard associated with the dump valve, if the result of a release from the dump valve will be a hazardous atmosphere or engulfment hazard, must be eliminated by utilizing the techniques described in the definition of the term "isolation". See the response to questions number one and two for further clarification of requirements related to elimination of hazards.

The tank described in your example "b" cannot be entered under the alternative procedures permitted by paragraph (c)(5) unless continuous ventilation is provided. Additionally, the alternative procedures described in paragraph (c)(5) can be implemented in permit-required confined spaces in which the only hazard is an actual or potentially hazardous atmosphere. If the input or output for the dry material can cause or permit material to enter the tank and create an engulfment hazard the techniques described in the definition of the term "isolation" must be used in order for the hazard to be considered eliminated. See the response to question number three for further information relative to use of the alternative procedures.

The underground vault/pit described in your example "c" cannot be reclassified as a non-permit required confined space unless all the hazards associated with the space are eliminated. Since the only hazards in that space seem to be either atmospheric hazards or engulfment hazards the procedures described in the definition of the term "isolation" must be used to eliminate the hazards.. Underground vaults/pits have the potential for actual or potential hazardous atmospheres. Contaminants can enter such spaces and certain chemical reactions, such as oxidation, which can deplete the oxygen in such spaces. If atmospheric hazards cannot be eliminated and continuous ventilation is used to control them the procedures set forth in paragraph (c)(5) must be followed.

As indicated in the response to question number two water is not considered to be an atmospheric hazard. Water in a permit-required confined space such as a pit can be an engulfment hazard or a hazard because it creates or conceals other unsafe conditions. If water in a permit-required confined space presents an engulfment hazard then the procedures described in the definition of the term "isolation" must be utilized.

If you require any additional information regarding the preceding, please contact Don Kallstrom by telephone at (202) 219-8031.

Sincerely,



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


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