Buyer beware...there is a lot of fraud in the market of air compressors. There are companies claiming more CFM than what their unit actually has. The way to check for this, get their PUMP-UP time in writing and this will cover you if they have a fault CFM. Things to watch out for: fast pump RPM--low RPM is better, compressor companies are giving you "starting" HP instead of "running" HP, which means NOTHING when purchasing a compressor. To be a TRUE 5 hp motor, it must pull at least 23 running amps or it is not a 5 hp motor. Compressor pumps that are claiming cast iron and they are really not. When shopping take a magnet with you. If it doesn't stick, it is not cast iron. Watch out for reed valves. They are a cheap valve system.
I swear by these compressors. Check out this site:
http://www.eatoncompressor.com/catalog/item/504747/206953.htm
