Singapore legislation
Regulation 82
of Workplace Safety and Health (Construction) Regulations 2007
Regulation 82
Ventilation
In a worksite where tunnelling works are carried out —
(a)
all work areas in a free air tunnel shall be provided with appropriate ventilation system to ensure adequate supply of fresh air;
(b)
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 —
(i)
at least 19.5% oxygen by volume; and
(ii)
not more than 23.5% oxygen by volume; and
(c)
air that has passed through any underground oil or fuel storage areas shall not be used for ventilation in the tunnel.