In the beginning of the episode, as enemy fire is coming through the Stargate, General Hammond orders the gate-room blast doors to be closed. The blast doors begin closing, but in the following shot of Hammond, the blast doors still wide open.
When the bomb is being prepared, we see two standard gas cylinders. One is labeled Hydrazine and the other is Liquid Oxygen. LOX is a cryogenic liquid that boils at -362°F and must be stored in a proper container. If there were LOX in the cylinder, it would be covered with a very thick layer of frost.