Tech. Sgt. John Mills-Hearne, a painter with the 459th Reserve Air Refueling Wing, has his protective mask straps adjusted before being exposed to a chemically filled room Jan. 23, 2013 at Joint Base Andrews, Md. Bioenvironmental engineers are required to sample air on location to help monitor the amount of chemicals workers are exposed to. (U.S Air Force photo/ Airman 1st Class Erin O’Shea)