Note the differences in confined spaces to follow the right standard
Working in a confined space can be hazardous but working in a permit-required confined space (permit space) is often downright dangerous. That’s why it’s important that employers ask the question: Is the work done in the permit space considered a maintenance or construction activity? The answer to that question will determine if OSHA’s 29 CFR 1910.146 general industry standard or the 1926 Subpart AA standard must be followed.

There are several OSHA Letters of Interpretation (LOI) that will help an employer answer the maintenance or construction question.

11/18/2003 - Clarification of maintenance vs. construction activities


This letter of interpretation states that “Construction work is not limited to new construction but can include the repair of existing facilities or the replacement of structures and their components. For example, the replacement of one utility pole with a new, identical pole would be maintenance; however, if it were replaced with an improved pole or equipment, it would be considered construction.”




02/01/1999 - The difference between maintenance and construction


This letter of interpretation defines maintenance as “… keeping equipment or a structure in proper condition through routine, scheduled or anticipated measures without having to significantly alter the structure or equipment in the process. For equipment, this generally means keeping the equipment working properly by taking steps to prevent its failure or degradation.”

02/01/1996 - Contractors and the criteria for applying the Construction Work Standard


In 1993, OSHA per 1910.12(a) required that all employers and employees engaged in construction work follow the regulations in 1926. 1910.12(b) defines construction work as “… work for construction, alteration, and/or repair, including painting and decorating.”

Know the difference


Confined spaces are different from permit-required confined spaces. A confined space is a space that:

● Is large enough and so configured that an employee can bodily enter and perform assigned work, and
● Has limited or restricted means for entry or exit, and
● Is not designed for continuous employee occupancy.

A permit-required confined space (permit space) is a confined space that has one or more of the following characteristics:

● Contains or has a potential to contain a hazardous atmosphere;
● Contains a material that has the potential for engulfing an entrant;
● Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section; or
● Contains any other recognized serious safety or health hazard, such as unguarded machinery, exposed live wires, or heat stress.

If the work employees are performing in the confined space is considered construction, then the 1926 Subpart AA standard must be followed. Subpart AA is generally considered more stringent than general industry’s 1910.146.


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