To turn off the AIR's output, unscrew the front grub screw. It's best to do that and relieve all the pressure in your marker before storage (i.e., you're better off not leaving your marker gassed up). You can buy an inline on/off for your macro that would kill the air supply to the marker, but that only seals off the hose, it doesn't reduce or eliminate the output pressure of the AIR reg, the only way to do that is to unscrew the front grub screw.