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Confined Space Definitions

OSHA’s confined space regulations defines the following terms.

► Confined Space

OSHA defines a confined space as any space in which the following three conditions exist concurrently:1. The space is large enough and so configured that an employee can bodily enter and perform assigned work; and,
2. The space has limited or restricted means for entry or exit; and,
3. The space is not designed for continuous employee occupancy. Examples of spaces which qualify as confined spaces under the OSHA definition include, but are not limited to: pipelines, storage tanks, vaults, vats, process vessels, catch basins, digesters, sewers, passageways, bins, boilers, pits, tank trucks, hoppers, tunnels, cargo holds, and excavations deeper
than four feet.


► Permit-Required Confined Space

A permit-required confined space is any confined space that has one or more of the following characteristics:
1. The space contains, or has the potential to contain, a hazardous atmosphere;
2. The space contains a material which has the potential for engulfing an entrant
3. The space 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,
4. The space contains any other recognized serious health or safety hazard.


► Non-Permit Confined Space

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.


► Hazardous Atmosphere

An atmosphere is hazardous when it contains:

1. < 19.5% oxygen (O2 deficient) or > 23.5% oxygen (O2 enriched);
2. A flammable gas, vapor, or mist at a concentration greater than 10% of its LEL (Lower Explosive Limit);
3. A toxic material at a concentration greater than its PEL (Permissible Exposure Limit);
4. A combustible dust at a concentration greater than its LEL, which may be approximated as a condition in which the dust obscures vision at a distance of 5 feet or less; or
5. Any other atmospheric condition which is IDLH (Immediately Dangerous to Life or Health)


► Immediately Dangerous to Life or Health (IDLH)

IDLH means any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual’s ability to escape unaided from a permit space.

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Confined Space Definitions