DenaturedAlcohol
+1y
What he means is the air traveling through the valve will pick up at the least the vapor of what ever product type you use and carry it to the bag. Make sure that what you use is ok for the seals in your valves, wont degrade the rubber your bags are made out of, wont corrode your fittings, and wont rust out your tank or damage any other component dealing with the transfer of the air through the system. You certainly do not want to use WD40. That stuff is bad news and once you atomize it out of your valves it will have the seals in it eaten up may even blow your fittings.