Mr Fix It Plumbing 4320 Atlantic Ave #230, Long Beach, CA 90807 (562) 988-2454 http://www.mrfixitplumbing.com/ A combustion air opening within an exterior wall of one-square-inch for each 4000 Btu rating of h2o heater is necessary throughout the upper and decreased 12 inches with the enclosure. Sign up for City https://www.google.com/maps?cid=4067949459714107514