Tech. Sgt. John Mills-Hearne, a painter with the 459th Reserve Air Refueling Wing, is observed by Airman Thomas McMahon, 779th Aerospace Medicine Squadron bioenvironmental engineering technician, as he demonstrates the proper painting techniques on an aircraft Jan. 23, 2013 at Joint Base Andrews, Md. Bioenvironmental engineers are required to sample on location to help monitor the amount of chemicals workers are exposed to. (U.S Air Force photo/ Airman 1st Class Erin O’Shea)