While visiting a viewer's basement we discovered two very dangerous things. She had mentioned that she had a heating duct that was disconnected. As we doug out the boxes and hanging coats that were in the way, we discovered a burn mark across a plastic coat cover as well as a burn right into the fur coat. It was hanging in contact with the flue pipe from the hot water tank. Always keep such an area clear. Then the "disconnected heating duct" turned out to be the hot water tank flue pipe itself, probably knocked out of place by all the stuff in storage. There it was, dumping all of it's toxic exhaust gass all year long right into the basement! Don't store things close to combustion appliances, and do check your flue pipes regularly.