The air solenoids will only be for the taper blast and the tool changer and should not be leaking any where unless it has air to clear the front bearing seal which can run all the time
You have 2 air connections up top on the side of the spindle ( 1 ) is for the Tool Changer and ( 1 ) for the air blast to clean the Taper, if the air is running all the time on the Taper Blast then you have a problem with the solenoids, as this should shut off before a tool goes back in