SEATTLE — The new State Route 99 tunnel under Seattle is two miles long, yet it contains 15 miles of lights, nearly 100 miles of wiring, and 21 miles of sprinkler piping. 

Those big yellow stacks you see atop both the south and north operations buildings are there for one purpose, to quickly evacuate any smoke from inside the tunnel in the case of a fire.

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Fans constantly push fresh air into the tunnel as other vans create positive air pressure along the western passageways to provide a safe haven for drivers if they have to seek refuge. 

Join us for a trip behind the scenes in the new tunnel that takes 34 people to maintain.

WATCH: Tour the Seattle tunnel before it opens

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