Hi,
When my central ac first comes on each time there is a brief puff of hot stale air. It lasts about 20 seconds then goes away and the air blows cold. Is this a symptom of a leak in the duct work or a problem with the compressor. The stale air doesn't smell good, faintly of coolant.
Thanks,
Cass

I don't know why the air would be hot or stale but, it will take a minute or two for the air to get cold. When the outside condensing unit comes on it has to pump liquid refrigerant into your inside unit were the liquid will be metered into the evaporator coil. It's normal for it to take a couple of minutes before you will feel the cold air. Have you had your evaportator coil cleaned or checked? It may be dirty and need cleaning.

Most of the newer AC's have installed a time delay to overcome the problem that JackT described. The heat also could be coming from insulation that has come off your duct system and the hot air in the attic is heating up the duct work.