Abstract: The present invention may be embodied as a system and/or a computer-based method for determining safe operation of a breathing gas system comprising the step of receiving a present oxygen concentration value from an oxygen concentration sensor. The method further comprises the step of receiving, at the computer, a present altitude value from an altimeter of the aircraft and using the computer to calculate an alarm flow rate, where the alarm flow rate is a function of the present oxygen concentration value and the present altitude value. The method may further comprise the step of receiving, at the computer, a present flow value from a flow meter, where the present flow value represents the rate of flow of breathing gas to the user. The method may comprise the step of comparing the calculated alarm flow rate to the received present flow value to determine a safe operation of the oxygen system.

Abstract: The present invention may be embodied as a system and/or a computer-based method for determining safe operation of a breathing gas system comprising the step of receiving a present oxygen concentration value from an oxygen concentration sensor. The method further comprises the step of receiving, at the computer, a present altitude value from an altimeter of the aircraft and using the computer to calculate an alarm flow rate, where the alarm flow rate is a function of the present oxygen concentration value and the present altitude value. The method may further comprise the step of receiving, at the computer, a present flow value from a flow meter, where the present flow value represents the rate of flow of breathing gas to the user. The method may comprise the step of comparing the calculated alarm flow rate to the received present flow value to determine a safe operation of the oxygen system.

Abstract: An adapter for use with a gas filter canister worn by a user as part of a breathing apparatus. The adapter is constructed of a semi-rigid plastic that has a plurality of scalloped or castellated edges. The scalloped or castellated edges allow the adapter to snap-fit over the top of the canister. Projections or lugs on the inside of the edge of the adapter can deflect and snap over the rim of the canister. An adapter seal in the form of a large preformed packing or O-ring, is pressed between the inside of the adapter top and the outside of the canister top such that an airtight seal is formed. The adapter is capable of moving relative to the filter canister to accommodate different positions of the flexible conduit between an adapter inlet and the outlet of a self contained blower assembly.