Won't start

if the propane cylinder is almost empty you maybe getting a concentration of murcapton(spelling?)this odorant is added to propane so it has an odor.when the gas gets low in the cylinder you can pull more odorant that may have settled in the bottom of the tank over time. there are other reasons since you are dealing with an unvented heating product , such as other odors fron oils,cleaning products, paint, etc. there could other problems so you may want to take it to your local propane store. jr