Self-contained breathing system
A breathing apparatus is operable in self-contained and filtered modes of operation. In the self-contained mode of operation, a breathable gas is delivered to a user from a self-contained source of breathing gas. In a second, filtered mode of operation, a suction source draws ambient air through a filter removing contaminants and delivers filtered ambient air to the user. A method of delivering air to a subject is also provided.
1. A breathing apparatus, comprising:
a conduit defining a passageway for a breathable gas having a first inlet for receiving breathable gas from a pressurized source of breathing gas, a second inlet for receiving filtered ambient air, and an outlet for delivering breathable gas to a user;
a suction source in fluid communication with said second inlet for drawing ambient air into said passageway;
a main filter assembly positioned between said second inlet and said passageway for removing contaminants from said ambient air;
a prefilter assembly positioned upstream of the main filter assembly, said prefilter assembly including one or more prefilter elements, said prefilter assembly including a prefilter housing receiving said one or more prefilter elements, said prefilter housing movable between a closed position wherein said second inlet is closed to ambient air and an open position wherein said second inlet is open to ambient air;
a pneumatically operated piston reciprocally movably within a cylinder, said piston mechanically coupled to said prefilter housing;
a normally closed passage extending between said cylinder and the pressurized source of breathing gas; and
a valve for selectively opening said normally closed passage to deliver pressurized breathing gas to said cylinder, wherein when the prefilter housing is in the open position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the closed position and wherein when the prefilter housing is in the closed position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the open position.
2. The breathing apparatus of claim 1 , further comprising:
a face mask adapted to be worn over a user's face and having a connection port; and
an air hose having a first end removably connected to said face mask connection port and a second end opposite the first end removably connected to said outlet.
3. The breathing apparatus of claim 2 , further comprising one or both of:
a purge valve connected to said first end of said air hose, the purge valve fluidically connected to said first stage regulator and manually actutable to provide a burst of regulated air from a first stage regulator; and
an alarm system for providing a user-perceptible alert when a pressure of the self-contained breathing system falls below a preselected value.
4. The breathing apparatus of claim 2 , wherein said air hose comprises an inner perforated hose for delivering air to a user and an outer flexible bag which is inflatable to hold a volume of air for subsequent delivery to the user.
5. The breathing apparatus of claim 1 , wherein said one or more prefilter elements includes:
a first prefilter element formed of a woven nylon material; and
a second prefilter element formed of a mesh filtration medium.
6. The breathing apparatus of claim 5 , wherein said mesh filtration medium is adapted to filter particles having a size of about 10 microns or larger from the ambient air.
7. The breathing apparatus of claim 1 , further comprising:
one or more self-contained sources of breathing gas removably attached to said passageway and selectively fluidically coupled to said first inlet.
8. The breathing apparatus of claim 1 , wherein said normally closed valve is a solenoid valve.
9. The breathing apparatus of claim 1 , wherein said main filter assembly is positioned between said second inlet and said suction source.
10. The breathing apparatus of claim 1 , wherein the passageway is sealed against entry of one or both of water and environmental contamination when the prefilter housing is closed.
11. The breathing apparatus of claim 1 , further comprising:
an actuator for activating the suction source when the prefilter housing is in the second position and deactivating the suction source when the prefilter housing is in the first position.
12. The breathing apparatus of claim 1 , further comprising:
a pressure sensor for detecting a pressure indicative of a quantity of gas remaining in the self-contained source of breathing gas; and
said valve operable under programmed control responsive to detected pressure reaching a preselected minimum threshold value.
13. The breathing apparatus of claim 1 , further comprising:
a pressure regulator for receiving pressurized gas at a first pressure and outputting the gas at a second pressure lower than the first pressure;
said valve in fluid communication with said pressure regulator.
14. The breathing apparatus of claim 1 , wherein the main filter assembly includes a main filter selected from a chemical, radiological, or biological filter, or any combination thereof.
15. The breathing apparatus of claim 1 , further comprising:
said conduit defining a passageway including a housing defining an internal cavity, the internal cavity providing a reservoir of breathable gas.
16. A breathing apparatus, comprising:
a conduit defining a passageway for a breathable gas having a first inlet for receiving breathable gas from a pressurized source of breathing gas, a second inlet for receiving filtered ambient air, and an outlet for delivering breathable gas to a user;
a suction source in fluid communication with said second inlet for drawing ambient air into said passageway;
a main filter assembly positioned between said second inlet and said passageway for removing contaminants from said ambient air;
a prefilter assembly positioned upstream of and in series with the main filter assembly, said prefilter assembly including one or more prefilter elements configured to trap particles in ambient air drawn into said passageway before it flows to said main filter assembly, said prefilter assembly including a prefilter housing receiving said one or more prefilter elements, said prefilter housing movable between a closed position wherein said second inlet is closed to ambient air and an open position wherein said second inlet is open to ambient air;
a pneumatically operated piston reciprocally movably within a cylinder, said piston mechanically coupled to said prefilter housing;
a normally closed passage extending between said cylinder and the pressurized source of breathing gas; and
a valve for selectively opening said normally closed passage to deliver pressurized breathing gas to said cylinder, wherein when the prefilter housing is in the open position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the closed position and wherein when the prefilter housing is in the closed position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the open position.