ProCom and Williams are companies that manufacture ventless gas heaters, as of 2015. Enerco Corporation manufactures ventless gas heaters under the name of Mr. Heater for home use and Enerco Technical Products for commercial and industrial use.
ProCom is one of the leading manufacturers of vent-free appliances in the United States. The company has 1.5 million square feet of manufacturing facilities in China, and has its corporate headquarters in Brea, California.
Williams started manufacturing heaters in 1916, in Los Angeles, California. Williams manufactures its products at the company's 400,000 square-foot complex in Colton, California. Enerco is located in Cleveland, Ohio, and has been manufacturing heaters since 1955.