Airman 1st Class Zachary Piper, 28th Medical Operations Squadron bioenvironmental engineering technician, lights a match to create carbon monoxide particles to be evaluated by a Porta Count machine during a gas mask fit test at Ellsworth Air Force Base, S.D., July 1, 2013. The burning of the match creates carbon monoxide so that the machine can count to determine if there are any leaks in the mask, and determine if the mask fits correctly and functions properly. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)