Originally Posted by kimconyc

Some people don't want to carry that though. I don't know about you but if I go through 2-3 CO2 and get a 4th flat on 1 ride, regardless of whether or not I'm carrying a pump in my back pocket, it's probably not a ride that's worth it...

But to answer the OP, blow on the valve stem as others have suggested. I also recommend keeping the bad tube so you can patch it up as an emergency in case the new one flats or is defective (happens).

I usually carry 1 tube and 3 CO2.