[Newellin Thunder]

You can disconnect the hose when the tank is pretty much empty and it's a good idea to purge it with some Nitrogen or other readily available non-oxygen carrying gas (argon, CO2). This is best done by a professional, as the cost of a mistake is pretty high. When you disconnect the hose fitting and open the valve to vent all of the gas, an emergency valve will close, restricting the escape of propane.