Though there is no water in the tetrafluoroethane (R-134a, eg Sara Lee Endust, Dust-Off Special Applications and many others) or difluoroethane (R-152a, "Dymel", eg standard Dust-Off), it does come out cold because it is evaporating and expanding (exactly how it works as a refrigerant) and it can, therefore, cause condensation in certain circumstances - though that may not matter. It could also cause local thermal stress.The usual reason for the warnings may be more to do with the speed, and hence the force, of the jet. Neither of these things are problems if the nozzle is kept sufficiently far from a delicate surface, but you don't need the force of 'canned air' for delicate surfaces, so why not just stick with an eco-friendly, airline-safe bulb like the Giottos Rocket already mentioned?
Best,
Helen