Used to (still kinda is) used by firefighters to test the seal on your SCBA mask. Put your mask on, put a hood on, spray Bitrex into the hood. Though mostly no

Used to (still kinda is) used by firefighters to test the seal on your SCBA mask. Put your mask on, put a hood on, spray Bitrex into the hood. Though mostly now we test via computer and a pump and measure vacuums.