With the cold weather approaching it is a great time to make sure your greenhouse heating system is working properly. Take the time to dust it off the unit, this should generally suffice if you use an electric heater. If your system runs off of propane, open your vale and check for leaks (use a dish washing liquid to do this; if it bubbles it is leaking). If a leak is detected, call a greenhouse heating professional to have the unit serviced. If you have oil heat, change your fuel filters and also check your lines for oil leaks, the lines will be wet and smell of oil they are leaking.