Often times when gas furnaces are installed in the attic, the gas pipe feeding the furnace is not properly supported. Home owners tend to use the attic for storage leaving the gas pipe vunerable to being stepped on or have items placed on top of it putting pressure on the pipe fittings as well as the gas valve in the heating unit causing a leak or cracked valve. The gas pipe should be properly supported either from the rafters or wooden blocks placed on the attic floor.