Adequate ventilation is essential for maintaining breathable air quality inside tunnels during construction. Without effective ventilation, diesel fumes from plant, dust from excavation, and ground gases accumulate to dangerous levels. The ventilation system must supply fresh air to the tunnel face and extract contaminated air continuously throughout all working hours. Ventilation failure is a potential life-threatening emergency requiring immediate evacuation. No one should enter a tunnel where ventilation is not operating.
Key Hazards
Oxygen depletion from diesel exhaust and ground gas displacing breathable air
Toxic fume accumulation from diesel plant operating in the confined tunnel space
Dust concentrations exceeding safe limits during excavation and shotcreting operations
Ground gas ingress including methane and carbon dioxide from surrounding geology
Control Measures
Ensure the tunnel ventilation system is operating and verified before any person enters the tunnel.
Monitor air quality continuously at the tunnel face using fixed and portable gas detection equipment.
Maintain oxygen levels above 19.5% and below the short-term exposure limits for all monitored gases.
Use low-emission diesel plant or electric alternatives to reduce exhaust fume generation in the tunnel.
Ensure ventilation ductwork is undamaged and extends to within a specified distance of the tunnel face.
Restrict the number and duration of diesel plant operations inside the tunnel to minimise emissions.
Provide RPE as specified by the air quality monitoring results when engineering controls are insufficient.
Display real-time air quality monitoring data at the tunnel portal for all workers to check before entry.
Evacuate the tunnel immediately if ventilation fails or air quality readings exceed safe limits.
Emergency / Rescue
If ventilation fails or air quality alarms trigger, evacuate the tunnel immediately via the nearest escape route. Report to the surface muster point. Do not re-enter until ventilation is restored and air quality confirmed safe.
Remember
The ventilation system is the lifeline for everyone working underground in a tunnel.
Never enter a tunnel where the ventilation system is not operating or has recently failed.
Diesel exhaust in confined tunnel space depletes oxygen and produces toxic carbon monoxide.
Air quality must be monitored continuously at the face and readings displayed at the portal.
Ventilation ductwork must be maintained intact and extend close to the active working face.
Ventilation failure is an emergency requiring immediate evacuation of all tunnel personnel.