Book 24, Question 79
How do workers get fresh air in a long tunnel?
Digging a tunnel makes dust and engine fumes, so builders keep fresh air moving all the time. Huge fans push clean air through big tubes or duct pipes to the working end. Shafts, which are vertical holes to the surface, let stale air out. Sensors check the air for dust and harmful gases.
More fun facts
- Long road tunnels get fresh air in two main ways: air pushed along the tunnel, called longitudinal ventilation, or air fed in through ducts, called transverse ventilation.
- Longitudinal systems move air in the same direction as the traffic and add or remove it at a few spots, such as a shaft or the tunnel entrance.
- Many tunnels hang a row of powerful jet fans from the ceiling to push air through the whole tunnel.
- The Cumberland Gap Tunnel in the United States uses jet fans like these.
- With full transverse ventilation, ducts above, below, or beside the road blow in fresh air at regular spots along the tunnel.
- Other ducts pull out the stale air and fumes from cars.
Sources: fhwa.dot.gov
Questions kids ask
Why do tunnels need big fans?
Cars give off fumes, so fans bring in fresh air and push out stale air to keep drivers safe.