Scenario: Prisoners escape through a tunnel

[Joseph Adams]

Hey! I'm a writer and need some assistance with a *sorta* engineering related hypothetical question: 

A bunch of prisoners plan to escape a prison by digging a 200 foot tunnel to safety. They have pretty much all the time in the world, but the question is... will they run out of air? At what point does a tunnel need to have proper ventilation? 

 

[Road Guy]

100 FT is the normal distance at which a tunnel requires ventilation - probably less distance if the diameter is small

 

[Road Guy]

Also where do I send my invoice for professional services too?

 

[RBHeadge PE]

Hey! I'm a writer and need some assistance with a *sorta* engineering related hypothetical question: 

A bunch of prisoners plan to escape a prison by digging a 200 foot tunnel to safety. They have pretty much all the time in the world, but the question is... will they run out of air? At what point does a tunnel need to have proper ventilation? 

Reminds me of the historic escape from Stalag Luft III. One of the tunnels was over 100 m (300 ft) long and had 76 escapees in about 2.5 hr. It was "designed" with a throughput of 1 escape/min. Another was about 100 ft and had 3 successful escapees. As I understand it the POWs had tiny periodic air holes through to the surface. 

It was the basis for the movie The Great Escape. https://en.wikipedia.org/wiki/The_Great_Escape_(film)