[supercat]

I used to work in the old Douglas aircraft hangar at LAX; the ceiling was 37 feet to the lights and heaters and 40 feet to the sprinkler heads.

So getting the water to the pipes required about an atmosphere of pressure.

The sprinklers were triggered by a sensor array on the ceiling and an emergency trip-handle in the fire closet where a 120 cubic foot Nitrogen bottle was piped to the unloading valve against a spring closure.

What was the function of the N2 bottle?

[Old Professer]

It opened the valve and held it open against water pressure.

I think I misstated the volume of the room; it is, of course 800 cubic feet.