Ventilation maintains oxygen levels and dilutes flammable gases and fumes, and some dusts (coal and sulphide dusts among them) that can ignite within their explosive limits; mechanical ventilation additionally cuts hazardous contaminants, dust and fumes and can regulate humidity and temperature. A competent person should design the system to give adequate ventilation throughout the excavation, such as a tunnel under construction, possibly including localised extraction for dust, heat or fumes from excavating, large plant or plant maintenance. The design should allow ventilation equipment or ducting to be extended as the excavation advances so the working face keeps its air supply.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.