Less than 20 meters. According to the query Nanchang City Planning Bureau official website information, Nanchang City, the distance of the flue from the residence should be less than 20 meters, the smoke vent should be higher than the roof, building height greater than 15m, the height of the smoke vent should be greater than 15 m. Nanchang, referred to as "Hong" or "Chang", ancient name Yuzhang, Hongdu, is a city under the jurisdiction of Jiangxi Province, the provincial capital, the core city of the urban agglomeration around Poyang Lake. Nanchang, abbreviated as "Hong" or "Chang", anciently known as Yuzhang and Hongdu, is a prefecture-level city under the jurisdiction of Jiangxi Province, the capital of the province, the core city of urban agglomeration around Poyang Lake, and an important central city in the middle reaches of the Yangtze River in China as determined by the State Council.