Under the definitions of "confined space" in 1910.146(b), open topped spaces are provided as examples of confined spaces. However, OSHA did not include language to define the depth at which a pit or open tank becomes a confined spaces. In the Preamble to the standard, OSHA cited the ANSI Z117.1-1977 definition of confined space "as enclosures with limited access and egress, such as storage tanks, open-topped spaces more than four feet in depth with poor natural ventilation, and sewers." DOE Order 5480.4/A2, Attachment 2 lists ANSI Z117.1-1977 as a mandatory ES&H standard. Therefore, whenever the roof is more than four feet below the top of the tank, the space is defined by DOE as a confined space.
The OSHA confined space standard provides requirements for permit- required confined spaces. Permit required confined spaces are confined spaces (see definition of confined space) that also have one or more of the following characteristics: atmospheric hazard, engulfment hazard, entrapment hazard or other recognized safety or health hazard. This regulation does not regulate non-permit required confined spaces, although other OSHA standards and DOE Orders may apply.
1910.146 does not apply to non-permit confined spaces. 1910.146(b) defines non-permit required confined spaces as "a confined space that does not contain, or with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm". The Preamble provides some examples of non- permit required spaces including, vented vaults, motor control cabinets, and dropped ceilings. These spaces have either natural or permanent mechanical ventilation to prevent the accumulation of atmospheric hazards and they do not present engulfment or other serious hazards.
1910.146(c)(1) requires the employer to evaluate the workplace to determine if any spaces are permit-required confined spaces. The Preamble explained OSHA's intent to alert the employer to prevent unauthorized entry. The agency further notes that failure to identify permit required spaces properly has resulted in injuries and fatalities. One commentator objected to the initial survey because confined spaces change. NIOSH data presented in the Preamble supported the OSHA initial survey by summarizing 44 incidents, of which 37 involved failure to recognize that the operation involved a confined space.
No part of the regulation addresses any requirements for non-permit required spaces, except as noted in the paragraph below. In fact, the decision flow chart in Appendix A to the standard directs the user to other applicable OSHA standards if there are no permit- required confined spaces, as defined by 1910.146(b).
1910.146(c)(6) requires the employer to reevaluate a non-permit required confined space if there is a change that might increase the hazards to entrants. Under 1910.146(c)(7), the employer can reclassify a permit space as a non-permit confined space if it poses no actual or potential atmospheric hazards and if all hazards within the space, are eliminated without entry into the space. If atmospheric hazards are controlled through forced ventilation, that does not constitute elimination of the hazards. The employer must document the space reclassification and make that reclassification certificate available to each employee who enters the space. If hazards arise within a declassified confined space, each employee shall exit the space and the employer must reevaluate the space, in accordance with the criteria in 1910.146.
With respect to entry into open-top tanks, if there is a potential for an atmospheric hazard, such as oxygen deficiency, then the space cannot be classified as a non-permit required confined space. The definition of "permit-required confined space" includes a provision for potential to contain hazardous atmospheres (1910,146(b)).
The inclusion of the phrase, "potential to contain a hazardous atmosphere", makes the standard a performance-based one because the employer must recognize spaces that may have the potential to contain an atmospheric hazard. In the Preamble, OSHA recognized that problems can arise when the employer has not selected the necessary atmospheric test instruments or has not ensured their proper use. Appendix B is non-mandatory, but does provide some guidance in evaluating the hazards of the permit space. It recommends that the evaluation be performed by a technically qualified professional.
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Last modified: 04/18/96 08:50:32