Wht wouldn't you use cedar for smoking. Haven't you heard of cedar plank salomn or fish in general. I not quite getting you on the sealing of the door thing with the cedar do you want to attach it to the door and make a seal out of it? I think I would use metal cause it won't burn. Need more info please.
Cedar is not recommended for smoking meats. Please read below for explanation.
Bad wood. Whatever you do, never use wood from conifers such as pine, fir, cyprus, spruce, redwood, or cedar. They contain too much sap and they can make the meat taste funny. Some have been known to make people sick. Yes, I know that cedar planks are popular for cooking salmon on, but I don't know anyone who burns cedar as a smoke wood. I have also heard that elm, eucalyptus, sassafras, sycamore, and liquid amber trees impart a bad flavor. Never use lumber scraps. Some lumber is treated with chemicals that are poisonous. Never use wood that has been painted. Never use wood that is moldy.