If you do a lot of Chinese cooking, which involves steam or strong odours, get a range hood rated at least 350 CFM. A ventilation rate of at least 1 CFM per 100 British Thermal Units (BTU) is recommended for high-efficiency gas stoves or ranges. For example, if your high-efficiency burner is rated at 45,000 BTUs, look for a range hood that provides 450 CFM to better clean the air.