Airman 1st Class Alexandra Aloba, 779th Aerospace Medicine Squadron bioenvironmental engineering technician, fills up a vile to monitor the amount of chlorine in a water sample Jan. 23, 2013 at Joint Base Andrews, Md. Bioenvironmental engineers are required to visit specific locations for testing once a month. (U.S. Air Force photo/ Airman 1st Class Erin O’Shea)