It is called NBC – nuclear, biological, chemical – warfare. First line of defense: gas masks. In boot camp, to drive home the lesson that a ill-fitting gas mask is a Bad Idea and that it’s a Good Idea to get that sucker in place Real Quick, this is what they make you do:
Strap on a gas mask carrier with gas mask inside.
Enter a building chock full of billowing clouds of tear gas.
Stand around for a few seconds while the instructor savors the moment.
Order you to don and clear.
If you get it right, the tear gas is on the outside of the mask.
If you get it wrong you have tear gas inside the mask with you and it fills up your lungs when you breathe. Or if you manage to clear but not seat the seal around your face it seeps inside when you breath and then fills up your lungs.