Any time you exhaust air out of your studio (be it in your house, garage or out-building), you need to provide replacement air from outside in equal amount to what is being exhausted.
The process of exhausting air forms a “partial vacuum” (also referred to as an area of lower pressure) inside the structure where the exhaust fan is located. Because of this “partial vacuum”, air will find any way it can to flow towards the fan.
We have talked a lot about “B” fittings on regulators, hoses and other parts, but what does ‘”B” fitting’ really mean?
In simple terms, the Compressed Gas Association (CGA) standardized fitting sizes some years ago. These fittings follow specific size and thread designs, and consist of “A”, “B”, “C” and “D” sizes. The welding industry for the most part uses “B” fittings, so those are the ones we will be discussing here. Also standardized is that oxygen fittings have right hand threads and fuel gas fittings have left hand threads. Fittings designed for use with fuel gas will also have a notch machined into either the nut or hex fitting.
Chaotic Glass by Mike Aurelius 
