air in it, and then they will demonstrate how to properly put it on their back, as well as their facepiece, and breathe air through it. >> and it's important because if it's damaged, it might fail when you're firefighting, and then you'd be in trouble, and you could possibly kill yourself. >> safety is part of every aspect of firefighting. even with just tying knots, you really have to know the ropes. >> they have basic fire knots they have to be able to tie. >> you have your bowline, your clove hitch, you have your half hitch, you have your becket bend. >> certain knots are designed to carry certain loads. >> if you don't tie the knot correctly -- if you're a hoisting a tool -- it might come loose and hit somebody in the head or injure somebody. >> even just putting up a ladder requires training and practice. it takes a whole other skill set to climb the aerial ladder, especially since this ladder can reach as high as a 10-story building. >> they go halfway up. at that point, they have a ladder belt that they tie into one of the rungs on the aerial ladder. on the aerial, stop and lock in.