What Counts as a Confined Space

A confined space is any space that is substantially enclosed, where there is a reasonably foreseeable specified risk — such as loss of consciousness from gas, fume, vapour or lack of oxygen, drowning, asphyxiation by a free-flowing solid, fire or explosion, or heat.

It is not about size

A space can be large and still confined. What matters is enclosure plus a specified risk.

Spaces routinely misclassified

• Open-topped pits, sumps and trenches — heavier-than-air gases accumulate at the bottom.
• Tanks with the lid removed — removing a lid does not ventilate a tank.
• Ship holds, silos and hoppers with free-flowing material.
• Ducts, culverts, sewers and interceptors.
• Unventilated plant rooms and cable tunnels.
• Spaces that became confined temporarily — a room purged with nitrogen, an enclosure erected for painting.

A space that is safe on Tuesday can be lethal on Wednesday. Classification is about the conditions, not the structure.