Airman 1st Class Joel Rogel, left, and William Raetz, 341st Medical Operations Squadron bioenvironmental engineering technicians, leave their building to perform a ventilation survey at the Auto Hobby shop April 8, 2015 at Malmstrom Air Force Base, Mont. Bioenvironmental routinely monitor 66 ventilation systems across the base to ensure safe working conditions. (U.S. Air Force photo/Chris Willis)