It is true that R-12 and most other refrigerants are heavier than air. If the air is still the gas will naturally settle in low areas, but it does not take much of a wind or thermal updraft to move the refrigerant around and disperse it throughout the atmosphere. As another poster mentioned, it is the chlorine in the refrigerants that does the harm, but only if it is separated from the rest of the refrigerant. In the upper atmosphere high intensity sunlight breaks down some of the refrigerant into its component parts and frees up the chlorine. This is not a problem that will go away quickly because most chlorine based refrigerants are very chemically stable and will take many, many years to be broken down. Also, the last I checked, chlorine based refrigerants are still being made and released into the atmosphere in large quantites by several third world countries such as China. Of course, any harm they due to the environment does not count since their economy is still "developing". /forums/images/graemlins/wink.gif /forums/images/graemlins/wink.gif