The experiments revealed that in open air, simulants decayed 10 to 1,000 times faster than in laboratory settings. These data indicate that laboratory tests underestimate the rate of agent decay that occurs outdoors, and on their own, laboratory tests are not sufficient in understanding the decay process outdoors. To learn how biological threat agents decay upon interacting with variables in the open air, the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department (DTRA CB) developed a new, state-of-the-art test apparatus, the Captive Aerosol Growth and Evolution System (CAGES). “Due to various challenges posed by outdoor testing, it was generally assumed by scientists that biological threat agents aged and decayed at similar rates indoors as they did outdoors. Our goal was to test this theory,” said Richard Mathieson, Science & Technology Manager, DTRA CB.