Mr Fix It Plumbing 4320 Atlantic Ave #230, Long Beach, CA 90807 (562) 988-2454 http://www.mrfixitplumbing.com/ A combustion air opening in an exterior wall of 1-sq.-inch for each 4000 Btu rating of water heater is necessary within the upper and decreased twelve inches in the enclosure. Make sure your h2o https://maps.app.goo.gl/JAqevuQwVnnK5SJu6