The CAS Air System is a breathing mask for firefighters. Firefighters face much greater risk for many types of cancer, including testicular and prostate cancer. They also have a higher risk of having children with congenital heart disease.  These risks increase when they do not use the SCBA (self contained breathing apparatus).  The CAS Air System allows firefighters to breathe easier than with a filter mask, and facilitates communication through the transparent window and a voice amplifier. A tube with compressed air kicks in automatically if the carbon monoxide level suddenly increases and warns the firefighter with a signal.