2-2-Air-Valves; this page is about what are they and how can they used in a compressed air circuit or for simple air operations.
Let's identify what a 2-2-air-valves is, first.
If a compressed air valve is identified as a 2-2 air valve, or perhaps it is written as 2/2 air valve, these numbers indicate the following about that particular air valve:
If the "at rest" position results in the air valve being closed (compressed air is not flowing from the in to the out port) then this valve is deemed to be an NC valve - one that is normally closed.
If, at the "at rest" position compressed air flows from the in port through the valve to the out port, then this valve is deemed to be an NO or a normally open valve.
For most applications the NC form of an air valve is selected, as most folks would want a compressed air valve that is shut off when the valve is at rest.
This could be an operator pushing a button or lever, a moving object depressing a toggle or whisker switch, or electricity operating a solenoid actuator on that air valve.
The blow gun contains (or is in itself) a 2/2 NC compressed air valve.
When the external actuator (the trigger or button) is actuated by an operator, air will flow from the supply side out the nozzle to do work.
When the actuator is released, the internal actuator (the spring inside the gun) moves the internal seals back into place to stop the air flow.
You can see from the photo that the blow gun's working port is the gun barrel, and it has no stop on the end. The barrel is open to atmosphere.
That means that when the actuator is released, supply air stops flowing, and the compressed air that is in the gun and barrel of the blowgun continues to vent to atmosphere until pressure is gone.
This is a typical type of application for 2-2-air-valves. The air taht is flowing through the 2/2 valve vents to atmosphere, not into some sort of closed container, where the air could be trapped when the valve is shut off.
2/2 air valves are commonly used in any application where the compressed air flows through the valve to atmosphere.