Clean Dry Air (CDA) is essential to ensure the aerosol is free of dust, water, and oil. Use filtered compressed air or canned compressed air, which is available at any laboratory supplier or photo/camera shop.
All "canned air" has a liquid propellant and may leave a residue unless you 1. hold them perfectly level when spraying and 2. spray for 3-5 seconds before using to insure that any liquid propellant is expelled from the nozzle.
These cans can be used to blow dust out of bulkheads with a connector in the other side or an active device mount (xmit/rcvr). NEVER use compressed air from a hose (they emit a fine spray of oil from the compressor!) or blow on them (you breath is full of moisture , not to mention all those germs!)