There are 3 parts of heat loss for gas boiler , including heat emission loss , uncompleted burning loss and fume hot loss , uncompleted burning loss decreases following the increase of excess air coefficient , while fume hot loss increases . it is obvious that there exit an optimum coefficient of excess air which make boiler own highest efficiency which is the purpose of burning control 不完全燃燒熱損失隨過量空氣系數的增大而減小,而排煙熱損失隨過量空氣系數的增大而增大,不難看出,存在一最佳的過量空氣系數使得兩者之和最小,即使得鍋爐的熱效率最高,燃燒控制的目的即在于此。