Propane tank

I will assume this is your house tank? If you have trapped air, you will need to purge the line before trying to start your furnace or other appliance. If you have a shut off valve OUTSIDE the house, loosen the flare fitting and bleed the air until you can smell gas. DO NOT DO THIS INSIDE THE HOUSE. When you can smell gas, tighten the fitting and then go inside the house and try to start the furnace,range or dryer, if gas. Ultimately they will start but it will take a while to get all the air out.