How it works
This is a test blast picture taken in Area 51 in Neveda.
Biological attack (gas release) chemicals being unseen and can travel airborne with wind currents thousands of miles from the impact zone.
  A typical bunker with a minimum of (6) six foot of earth with an intake and exhaust vent pipe with a screen covered  turn down.
Why so deep?
To prevent death from high heat inside the safe area caused by the heat wave blast (50-75 mile radius from impact).
  Our system should be installed inside your safe area where filters can easily be accessed for replacement. (making the filters room side replaceable).
  The system should be attached with a metal flex-duct connecting  the air intake which leads in from the outside of the safe area , to the upstream connection of our system to draw contaminated air into the system.
  The filters are designed to trap all contaminates and allow only clean filtered air to pass through and into your safe area.
  Factory installed Magnehelic gages show the operator each filter's pressure drop or how loaded or dirty the filters are becoming during operation. Gages are equipt with filter change-out flags which when indicated, system should be shut down and new filters installed.
  A typical home made bunker constructed from a corrugated drain pipe with entrance, air intake & exhaust vent.