US Patent 7197774 Supplied air helmet having face seal with differentiated permeability

A supplied air helmet 10 comprises a visor 14 and a face seal 12 that is secured to the visor. The face seal 12 includes a sealing member 18 and a frame member 16. The sealing member 18 extends radially inward from the frame member 16 and has first and second regions of permeability 20 and 22. The second region 22 has greater permeability than the first region 20. The use of a face seal 12 that has differentiated permeability allows for a controlled flow of air through the interior of the supplied air helmet 10.