now using a compressor and blow tool to blow dust out of electronics is a bad idea.. the tank collects moisture which then goes through the line and out the blow tool. you should be using canned dry air sold in the computer section or electronics department
I was concerned about moisture in the compressed air also, but I tried it on a few things and found the small amount of water evaporates quickly. I've been cleaning computers and audio amplifiers with it for a couple of years and haven't had any trouble.
The "canned air" can cause condensation on parts, too, because it cools the parts. If you use canned air on a humid day you'll get condensation.
So I don't do it on humid days.
I considered buying a water separator for the compressed air, but after asking several colleagues, they all told me it was unnecessary. If I ever buy a larger shop compressor I would probably set it up with water and oil separation for cleaning, though.