Australia Model Work Health and Safety Regulations r70-73: rr 70 to 73 Isolate connected plant and services, control the atmosphere, flammables and ignition sources

The PCBU eliminates, or if not reasonably practicable minimises, the risk from substances or conditions introduced by connected plant or services and from their activation or energising (isolation and lockout); ensures purging or ventilation of contaminants so far as reasonably practicable without using pure oxygen or oxygen-enriched mixtures above 21%; ensures a safe oxygen level while work continues or, where that is not reasonably practicable and oxygen is below 19.5%, provides air-supplied respiratory equipment; keeps flammable gas, vapour or mist below 5% of the lower explosive limit so far as reasonably practicable, removing workers immediately at 5% to under 10% unless a calibrated continuous-monitoring detector is used, and at 10% or more in all cases; and prevents any ignition source being introduced where it could cause fire or explosion.