Permit Required Confined Space Definition (OSHA -29 CFR 1910.146)
A Permit-Required Confined Space is a space that:
is large enough and so configured that an employee can enter and performed assigned work; and
has limited or restricted means for entry or exit; and
is not designed for continuous employee occupancy; and
has one or more of the following characteristics:
Contains or has the potential to contain a hazardous atmosphere; or
Contains a material that has the potential for entrapping, engulfing or suffocating an entrant; or
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.