A backpressure-modulating cartridge for a breathing mask includes a body defining a first chamber which communicates with the environment, a second chamber which communicates with the mask, and a passage which communicates with the first and second chambers. A guide rod is supported by the body and is...http://www.google.fr/patents/US5937857?utm_source=gb-gplus-shareBrevet US5937857 - Backpressure-modulating cartridge for breathing mask
Backpressure-modulating cartridge for breathing mask
