1.   It became clear that American combat engineers had blown up an Iraqi weapons depot that contained chemical weapons, making it likely that dangerous vapors had escaped.

2.   These holes will allow trapped moisture vapor to escape harmlessly to the outside instead of condensing on the cold glass of the storm window.

3.   The fuel vapors escaped from a pipe that appeared to have a broken weld, damaged perhaps by the shock from the cold hydrogen.

4.   The fuel vapors escaped from a pipe that appeared to have broken or come loose at a fitting.