[The Permit Required Confined Space Entry Standard (1910.146) in paragraph (c)(5) allows an employer the option of developing alternate entry procedures. If an employer is to do this:

1. What documentation and testing is required?
2. If you have a number of spaces that are virtually identical, can a typical space be monitored and the results applied to other spaces?
3. Are calculations of volumes and flow rates acceptable in place of monitoring?
4. How many air changes per hour are required? What would be considered an acceptable rate?]

OSHA's National Headquarter's Office of Safety Standards was called for a response to the caller's four questions.

OSHA's confined space standard is performance based, meaning there is no specific requirement as to how and what must be documented. Before a person enters a confined space the internal atmosphere of the space is to be tested as stated, 29 CFR 1910.146(c)(5)(ii)(C). The air measurements made along with other pertinent information (i.e., time, date, who collected measurements etc.) should be recorded. OSHA indicated to record enough information in any format you choose so that in the event of an accident you could prove to an OSHA inspector that appropriate steps were taken before the employe(s) entered the space.

The spaces may be constructed the same, but unless the internal atmosphere is tested, there is no way to ensure that conditions are the same. Because the caller has asked about options if alternate procedures are implemented, internal atmosphere testing is a requirement (c)(5)(ii)(C).

Regarding the use of calculations of volumes and flow rates in lieu of sampling, it would not be acceptable because one of the criteria under the alternate procedures in (c)(5)(ii)(C) is to test the internal atmosphere of the space before employees enter. Also, (c)(5)(ii)(F) requires periodic testing of the air to ensure that the continuous forced air ventilation is preventing the accumulation of a hazardous atmosphere. Calculating the volume and flow rates would not satisfy the criteria under the alternate procedures.

This is a performance based standard and OSHA is concerned with results. The forced air ventilation must supply a quantity of air that is adequate to eliminate any hazardous atmospheres and prevent their accumulation. The atmosphere within the space must be periodically tested to ensure that the ventilation is preventing the accumulation of a hazardous atmosphere. Because the ventilation requirements are very site specific, depending upon the size and configuration of the space, the conditions in the space, the work being conducted in the space and the source of hazardous atmospheres, no general rule can be prescribed for numbers of air changes per hour. This will depend upon the specific circumstances of each confined space entry. The burden of determining adequate forced air ventilation is the employer's.

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Last modified: 04/18/96 08:50:32