a breathing device that is placed over the mouth and nose; supplies oxygen from an attached storage tank
a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
hide under a false appearance
activity that tries to conceal something
make unrecognizable
a protective covering worn over the face
