The Lennox Hearth fireplace plant in Union City is up for sale, according to a statement from the company. Lennox Hearth Products is based in Nashville and has manufacturing facilities in Union City, Auburn, Wash., and Laval, Quebec, Canada. The company announced it intends to sell three of its plants, including the one in Union City, due to low market demand. The Union City plant employs between 200 and 250 workers. The company has not announced when or if the sale would affect employees.