How much nitrogen do I need for an exit mask?

[Jason0941]

I can't decide whether I should get a 20 ft^3 cylinder, or a 40 ft^3 cylinder.

 

[Galahad]

For clarity, I'm taking about an exit bag rather than a mask. I have no idea what your mask setup is.

For an exit bag you require 15lpm, for an EEBD hood 25lpm is recommended for a minimum of 20 minutes.


20 cubic feet is 566 litres.

566 litres (20ft^3) would provide around 37 mins at 15lpm.

2 questions, is the larger cylinder much more expensive (ie still affordable) and is it too big for you to transport/conceal?

You may as well get the bigger one if it's no problem and apply the belt and braces mantra but the 20 should be ample.

 

[locked*n*loaded]

I'd say 40 cu ft (1133 liters) to be on the safe side.