Lt. Andre Slaughter inspects TSgt Robert Wise's gas mask during a gas mask fit test. The D.C. Air National Guard is replacing all MCU-2 A/P gas masks with the new M50 gas mask. The new M50 gas mask has twin conformal filters, which allow 50 percent improvement in breathing resistance, and allows for over 24 hours of protection against chemical or biological agents and radioactive particulate matter. (U.S. Air Force Photo by Tech Sgt. Gareth Buckland)