A pressure regulator assembly for an SCBA includes a valve assembly having a piston, a cylinder for receiving the piston, a sealing member for engagement by the piston, a conduit extending through the piston and facilitating fluid communication between an inlet chamber and a cavity of the cylinder, and a driving assembly for facilitating the engagement and disengagement of the piston responsive to a change of pressure in the outlet chamber. A bypass assembly for an SCBA is also disclosed.

Systems and methods for emergency breathing systems in accordance with embodiments of the invention are disclosed. In an embodiment, a second stage regulator includes a housing, a first nosepiece coupled to a first lever, a second nosepiece coupled to a second lever, a first spring located in the housing and coupled to the first nosepiece and the first lever, a second spring located in the housing and coupled to the second nosepiece and the second lever, a mouthpiece, and a coupler coupled to the housing, wherein the first spring and the second spring bias the first nosepiece and the second nosepiece towards each other.

A pressure regulator assembly for an SCBA includes a valve assembly having a piston, a cylinder for receiving the piston, a sealing member for engagement by the piston, a conduit extending through the piston and facilitating fluid communication between an inlet chamber and a cavity of the cylinder, and a driving assembly for facilitating the engagement and disengagement of the piston responsive to a change of pressure in the outlet chamber. A bypass assembly for an SCBA is also disclosed.

A pressure regulator assembly for an SCBA includes a valve assembly having a piston, a cylinder for receiving the piston, a sealing member for engagement by the piston, a conduit extending through the piston and facilitating fluid communication between an inlet chamber and a cavity of the cylinder, and a driving assembly for facilitating the engagement and disengagement of the piston responsive to a change of pressure in the outlet chamber. A bypass assembly for an SCBA is also disclosed.

A pressure regulator assembly for an SCBA including a valve assembly having a piston, a cylinder configured to receive the piston, a sealing member configured for engagement by the piston, a conduit extending through the piston and facilitating fluid communication between an inlet chamber and a cavity of the cylinder, and a driving assembly configured to facilitate the engagement and disengagement of the piston responsive to a change of pressure in the outlet chamber. A bypass assembly for an SCBA is also disclosed.

A demand regulator for a breathing apparatus may include a primary lever arm can include a cam element having a first profile and a second profile, the primary lever arm being pivotable; and a valve configured to regulate a flow of breathing gas through the demand regulator. The valve may include a valve member being displaceable so as to regulate the flow of breathing gas. The cam element of the primary lever arm is configured to displace the valve member during pivoting of the primary lever arm. Pivoting of the primary lever arm through a first arc displaces the valve member at a first displacement rate; and pivoting of the primary lever arm through a second arc displaces the valve member at a second displacement rate. A breathing apparatus can include a demand regulator and a diaphragm-actuated lever arm. A method for designing a cam element profile is disclosed.

A gas negative pressure valve is provided which comprises a valve body and a valve cover. A gas inlet and a gas outlet are disposed on the valve body. A drive lever and a diaphragm assembly are disposed inside the valve body, and one end of the drive lever is connected to a lower end of the diaphragm assembly, and the other end of the drive lever is connected with a sealing gasket. An end of the drive lever is hinged on a sidewall of the valve body. A reset spring is disposed between the drive lever and a bottom of an inner chamber of the valve body. A guide passage is opened in the inner chamber of the valve body. An end of the drive lever close to the gas inlet is connected with a guide shaft, a lower end of which is cooperated slidably in the guide passage.