I live in a low income rental that has a gas furnace & water heater. I went into the crawl space and found a 6" pipe about 3 feet long that comes from the outside. It is not attached to anything but the cold air rushes into the crawl space. I feel this might have been an error in installation. Also the heat ducts are not wrapped and are quite warm to the to the touch when the furnace is running. I think I've been heating the whole neighborhood! Also, is there a danger of carbon monoxide poisoning if this duct should have been attached to the furnace?