Air at any temperature and pressure will have a definite limit in the amount of water it can hold as vapor. Beyond that limit, water must condense out.
If air is initially saturated and then cooled or compressed, condensation will occur because the air cannot hold as much water in vapor form at the lower temperature and higher pressure.
Air at 2000 psia and 100F will hold about 22 lbm of water per mmscf if it is fully saturated. Cooling this air to a lower temperature will cause water to condense. At 90F the 2000 psi air will only hold ~ 16 lbm of water per mmscf. This is a lot less than the 3100 or so lbm of water that the same mmscf could hold at 100 F at atmospheric pressure.
