John, You're right.... There is a hell of a difference. You're probebly go to laugh..... But it depends on the manufacturer as to which was it is........ Always get them to specify which it is for the "particular" compressor you're looking at. If you look at the prices...... you'll see that there is a gap between the two varieties of ratings. The more expensive group, is the 8cfm at supply pressure (say 100 psi). Cheers, Phill. ----- Original Message ----- From: <john.pagett@xxxxxxxxxx> To: <modeleng@xxxxxxxxxxxxx> Sent: Wednesday, November 17, 2004 9:30 PM Subject: [modeleng] Yet another dumb question > Gents, > > This may sound daft, but I've never seen a decent description... > When an air compressor is rated at so many cfm (cubic feet per minute), > does that refer to air in its compressed state or at atmospheric pressure? > I reckon there's about a 7 or 8 to 1 difference! > > Thanks, > > JohnP > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email to, > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. > > > MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.