Underground mines, tunnels, and shafts

These spaces are intended for people to carry out work in them. This work is covered by specific regulation. They may present physical or atmospheric hazards. Many utilities are routed through tunnels or underground shafts where hazardous atmospheres may collect from containers or operations above or be created by utility leaks (such as gas and oil).
Work in shafts must be carefully planned. Because the work may be of short duration and require only a temporary platform, these jobs are often not given proper attention.
In addition to the areas already described, beware of apparently harmless areas such as basements, halls, and small rooms that can become dangerous when a lack of ventilation and hazardous materials or operations combine to create atmospheric hazards.

If a worker can be injured by inhaling a hazardous gas, vapour, dust, or fume or there is an explosion hazard then you must provide adequate ventilation by natural or mechanical means. If this is not possible then you must provide respiratory protection equipment suitable for the hazard.