Operators with the FBI HRT storm the second floor of a building during a training exercise.
These HRT operators are wearing C420 PAPR (Powered Air-Purifying Respirator) Systems on their backs, linked to CBRN C50 gas masks. Such gear protects the wearer from breathing Chemical Biological Radiological or Nuclear-contaminated air.
The HRT team has gained second-story access via an elevated tactical system (ETS), a height-adjustable ramp system fitted to a vehicle which can deploy tactical teams to above-ground-level stories of buildings and assault positions of hijacked airliners.
The FBI's Hostage Rescue Team is an elite tactical unit that provides a federal-level domestic counter-terrorism capability.