A method for determining a characteristic such as partial pressure or percentage of a gaseous constituent in a first gas mixture flow in a flow chamber in which there is alternating flow in opposite directions between the first gas mixture flow and a second gas mixture flow. The steps may include a) introducing the first gas mixture flow into a sensing chamber when the first gas mixture flow flows in the flow chamber, b) preventing introduction of gas from the flow chamber into the sensing chamber at least when the second gas mixture flow flows in the flow chamber, c) sensing the characteristic of the first gas mixture flow in the sensing chamber.

A bypass knob for a pressure regulator configured for use with a facemask of a breathing apparatus has a first member having a first engagement surface and a second member having a second engagement surface positioned opposite the first engagement surface. At least one slot is formed on the first engagement surface and at least one deflectable beam having a latch is formed on the second engagement surface of the second member. When the first member is rotated in a first direction about the longitudinal axis via a first rotational torque, the latch of the at least one deflectable beam is engaged with the at least one slot to rotate the second member with the first member, and disengaged when the first member is rotated in the first direction via a second rotational torque higher than the first rotational torque.

A personal breathing system incorporating a phased-dilution demand oxygen regulator (PDDOR) is disclosed. In embodiments, the breathing system includes a pressurized oxygen source and oronasal mask, a dilution valve for supplying ambient air and a demand valve for supplying pure oxygen. The PDDOR senses the mask pressure associated with the start of an inhalation cycle, maintaining pressure to the demand valve through an initial demand phase during which 100% pure oxygen is supplied through the demand valve. Control pressure within the PDDOR drops throughout the initial demand phase; when the pressure drops below a lower threshold the PDDOR main valve is closed, blocking the demand valve and cutting off the oxygen supply. Ambient air is provided to the mask via a dilution valve to preserve flow to the user.

A first stage regulator for two-stage delivering assemblies includes a first chamber connected through an inlet to a high pressure gas source; a second chamber for the breathable gas at an intermediate pressure, which is connected to a user; a pressure reducing valve connecting the first and the second chambers and having a valve seat and a cut-off that cooperates with the valve seat and is displaceable from a closed position to an open position thereof and vice versa. The cut-off is dynamically connected to a sensor exposed to the external pressure and includes a transmitting element of the mechanical stress exerted on the sensor by the external pressure. The sensor includes a movable wall that is sealingly slidable in a housing chamber and constitutes the interface wall towards the outside, and the transmitting mechanism connects the movable wall with the cut-off.

Disclosed is a modular serviceable cartridge assembly for a respirator exhalation unit that is simple in construction and that allows quick-connect of an exhalation valve cartridge in a mask to minimize the need for reconfiguration when changing personal protective equipment, and that allows for easy removal and breakdown for servicing and/or replacement of individual components of the exhalation valve without modifying or replacing other elements of the protective mask. The assembly may be convertible from a negative pressure valve assembly to a positive pressure valve assembly, and vice versa, and a grill may be provided on an outlet side of the cartridge assembly, the rotation of which converts the assembly from a negative pressure valve to a positive pressure valve.

An oxygen system supplies either 100% oxygen to a demand valve in a or pulses of oxygen to the mask. Switching is automatic during a parachute descent. The system includes a valve manifold that is responsive to ambient pressure such that at low pressures it is configured to deliver gas from either an oxygen cylinder or an aircraft supply line to the mask demand valve and at higher pressures it is configured to deliver gas from the cylinder to a pulse gas delivery system. The mask also includes an inhalation valve that is closed if oxygen is supplied to the demand valve. Otherwise, the inhalation valve opens to allow ambient air to be drawn in and the pulse gas delivery system delivers a pulse of oxygen in response to the onset of inhalation.

An oxygen supply system for delivering oxygen to passengers in an aircraft in an event of a loss of cabin pressure includes a source of oxygen, a passenger service unit, and a main controller. The passenger service unit includes a face mask configured to facilitate a flow of an accumulated volume of oxygen from the source of oxygen, and a sensor configured to detect at least one of an ambient pressure, an airflow in a first direction, or an airflow in a second direction. The main controller is configured to determine at least one of the ambient pressure, the airflow being in the first direction, or the airflow being in the second direction, and command delivery of oxygen from the source of oxygen to the face mask in response to the determination.

An oxygen system supplies either 100% oxygen to a demand valve in a mask or pulses of oxygen to the mask. Switching is automatic during a parachute descent. The system includes a valve manifold that is responsive to ambient pressure such that at low pressures it is configured to deliver gas from either an oxygen cylinder or an aircraft supply line to the mask demand valve and at higher pressures it is configured to deliver gas from the cylinder to a pulse gas delivery system. The mask also includes an inhalation valve that is closed if oxygen is supplied to the demand valve. Otherwise, the inhalation valve opens to allow ambient air to be drawn in and the pulse gas delivery system delivers a pulse of oxygen in response to the onset of inhalation.

Disclosed is a modular serviceable cartridge assembly for a respirator exhalation unit that is simple in construction and that allows quick-connect of an exhalation valve cartridge in a mask to minimize the need for reconfiguration when changing personal protective equipment, and that allows for easy removal and breakdown for servicing and/or replacement of individual components of the exhalation valve without modifying or replacing other elements of the protective mask. The assembly may be convertible from a negative pressure valve assembly to a positive pressure valve assembly, and vice versa, and a grill may be provided on an outlet side of the cartridge assembly, the rotation of which converts the assembly from a negative pressure valve to a positive pressure valve.

A bypass knob for a pressure regulator configured for use with a facemask of a breathing apparatus has a first member having a first engagement surface and a second member having a second engagement surface positioned opposite the first engagement surface. At least one slot is formed on the first engagement surface and at least one deflectable beam having a latch is formed on the second engagement surface of the second member. When the first member is rotated in a first direction about the longitudinal axis via a first rotational torque, the latch of the at least one deflectable beam is engaged with the at least one slot to rotate the second member with the first member, and disengaged when the first member is rotated in the first direction via a second rotational torque higher than the first rotational torque.