Nearly 18 million households are strong candidates for conversion to natural gas heating. So says the
American Gas Association (A.G.A.). The AGA estimates that 7.6 million natural gas customers don't use gas for heating and about 10.2 million households lack gas service, although it is available in their neighborhoods. To maintain its heating market dominance, the industry plans to promote the advantages of gas to homebuilders as well as to existing and potential customers.