82. Ventilation

In a worksite where tunnelling works are carried out —

all work areas in a free air tunnel shall be provided with appropriate ventilation system to ensure adequate supply of fresh air;

all reasonably practicable measures shall be taken to ensure that the air in the tunnel where a person has to work is free from flammable gases and vapours and contains —

at least 19.5% oxygen by volume; and

not more than 23.5% oxygen by volume; and

air that has passed through any underground oil or fuel storage areas shall not be used for ventilation in the tunnel.