When the bomb under the podium fails to go off, the killer gets a gun and screws on a silencer. He gets into a fight with Weller before he can shoot and drops the gun. During the fight, Weller picks up the gun, but the silencer is gone. When he shoots the killer, the silencer is back on.
There are several issues with the description of the bomb housing. Firstly it's not a pressure vessel as it isn't holding a massively disproportionate amount of gas to normal atmospheric pressure. The pressure gauge is reading 12.5 psi. Normal atmospheric pressure at sea level is 14.696 psi which is a marginal difference.
Furthermore, Dalton's law of partial pressure describes that gas will always flow from high pressure to low pressure environments, so a room at normal pressure would flood the housing for the bomb; the bomb would not see a deep in pressure from gas being released and detonate.
Furthermore, Dalton's law of partial pressure describes that gas will always flow from high pressure to low pressure environments, so a room at normal pressure would flood the housing for the bomb; the bomb would not see a deep in pressure from gas being released and detonate.