Abstract: A variable volume ratio compound counterlung is disclosed for use with a semi-closed circuit breathing apparatus. The compound counterlung generally comprises a flexible bag member disposed within and attached to an outer counterlung member. A pair of depth sensors are provided to vary the volume of said flexible bag member with changes in depth. The flexible bag member is driven by the outer counterlung to discharge gas stored within the flexible bag member depending on the diver's respiratory minute volume. The volumetric capacity of the inner counterlung is controlled by one or more ambient pressure sensing devices with an outer bellows-type counterlung that drives the inner counterlung's contents overboard with each breathing cycle.

Abstract: A variable volume ratio compound counterlung is disclosed for use with a semi-closed circuit breathing apparatus. The compound counterlung generally comprises a flexible bag member disposed within an outer counterlung member. The flexible bag member and the outer counterlung member are in communication with an exhaled gas area of a breathing loop. The flexible bag member having first and second ends which are attached to said outer counterlung. A pair of depth sensors operatively associated with the flexible bag member are provided to vary the volume of said flexible bag member with changes in depth. The flexible bag member is driven by the outer counterlung to discharge gas stored within the flexible bag member depending on the diver's respiratory minute volume. The collapsing of said outer counterlung member also returns gas stored within the outer counterlung back into the breathing loop.

Abstract: A balanced breathing loop for a rebreather is disclosed which includes a system of components that interact to provide substantial safety and alarm awareness benefits over existing methodology in recirculating breathing apparatus loops. The device relies on a specific arrangement of components to create both automatic alternate delivery of gas to replace metabolized oxygen in case of single component failures and breathing characteristic changes that warn the user that a component failure has occurred. The breathing characteristic changes allow the user to identify which specific component has failed, thus allowing for immediate corrective action.

Abstract: A variable volume ratio compound counterlung is disclosed for use with a semi-closed circuit breathing apparatus. The compound counterlung generally comprises a flexible bag member disposed within an outer counterlung member. The flexible bag member and the outer counterlung member are in communication with an exhaled gas area of a breathing loop. The flexible bag member having first and second ends which are attached to said outer counterlung. A pair of depth sensors operatively associated with the flexible bag member are provided to vary the volume of said flexible bag member with changes in depth. The flexible bag member is driven by the outer counterlung to discharge gas stored within the flexible bag member depending on the diver's respiratory minute volume. The collapsing of said outer counterlung member also returns gas stored within the outer counterlung back into the breathing loop.