If the seal if broken, you'll be choking
Staff Sgt. Shawn Gallagher, 2nd Aerospace Medical Squadron, reads information off a photocount plus machine during a gas mask fit test on Barksdale Air Force Base, La., May 9, 2013. During the test, a photocount plus machine measures the particle readings from the air in the room and compares it to the air found in the gas masks to ensure the masks are sealed properly. Gas mask fit tests, which are held every Thursday from 8 to 11 a.m. at Bio-Environmental Engineering, ensure Barksdale Airmen have the correct gas mask size to protect them from chemical and biological warfare agents. (U.S. Air Force photo/Airman 1st Class Benjamin Gonsier)