A lack of oxygen or oxygen deficiency can be caused by several processes. Which one of the following is correct?

Question

Accepted Answer

Oxygen is used up by the person who is in the confined space or by the activity in the confined space, and is turned into carbon dioxide.

Answer

Inside steel tanks and vessels when rust forms.

Answer

Build-up in sewers and manholes and in pits connected to the system enters tanks or vessels from connecting pipes.

Answer

Residues left in tanks or vessels, or remaining on internal surfaces, can give off gas, fumes or vapour.

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