[Recluse]

I think the converted hot water tank will rupture quite immediately.

[supercat]

I think the converted hot water tank will rupture quite immediately.

At 75PSI? Note that he did specify a regulator between the pressure tank and the water tank.

[Old Professer]

It will be fitted with a $125 precision regulator set to 75PSI output pressure; the sprinkler head will burn out and allow the compressed air to push the water as a wall through the pipe; when the water is gone the remaining air will flood the room and the moisture-laden air will sink to the floor.

Using CO2 or N2 would risk asphyxiation of occupants after the fire was out.

If the fire was allowed to burn with no abatement, everyone in the room would die or open the door and spread the fire to the rest of the building floor first and other floors next.