Spc. Richard Azevedo (right) and Spc. Jonathan Soto (left), both infantrymen, Headquarters and Headquarters Company, 1st Stryker Brigade Combat Team, 4th Infantry Division, wait for their turn in the gas chamber during annual chemical, biological, radiological and nuclear training, Jan. 8, 2015. The gas chamber is a confined space used to expose Soldiers to tear gas to build confidence in their M40-series protective masks.