0.8- 1.5 times. According to Tianzhu's inquiry. Com, the number of fresh air changes in beauty salons in civil buildings can be counted as 0.8- 1.5 times per hour from the economic point of view, while it is counted as 2-5 times in commercial areas. When the fresh air system is set separately and the air exchange volume is large, the influence of fresh air on heating load and air conditioning load should be fully considered. From the perspective of energy saving, it is appropriate to choose the all-heat exchange fresh air unit.