The United States of America As Represented by the Secretary of

Richard L Stein

Thomas E Bernard

A self-contained, closed circuit breathing apparatus having a balanced breathing resistance system is provided by an apparatus comprising an inhalation conduit and an exhalation conduit, a mouth connection communicating with said conduits for making connection with the mouth of the operator, an inhalation check valve and an exhalation check valve on either side of said mouth connection providing uni-directional flow through said inhalation and exhalation conduits, respectively, a chemical canister connected across said inhalation and exhalation conduits, a pre-canister storage container communicating with said exhalation conduit, said pre-canister storage container being provided with a uni-directional impedance component comprised of a resistance means for allowing one part of the exhaled air during exhalation to pass into the pre-canister storage container and the remainder to pass through said chemical canister into a post-canister storage container and a uni-directional check valve permitting essentially free flow of air out of said pre-canister storage container during inhalation and said post-canister storage container being provided with a uni-directional impedance component comprised of a uni-directional check valve permitting essentially free flow of air into said post-canister storage container during exhalation and with a resistance means permitting restricted flow of air from said post-canister storage container during inhalation.

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Pittsburgh, PA, United States of America

Richard L Stein