Traditional Culture Encyclopedia - Traditional stories - What kinds of hoods are there? Which works best?

What kinds of hoods are there? Which works best?

Common ones are louver covers, unpowered balloons and metal exhaust fans. The best effect is the Wanju suction hood, which uses the external natural airflow to drive the airflow in the flue to be discharged upwards, which has the effect of suction and obvious effect. However, unpowered balloons and louvers do not exhaust upward, which will form air resistance and easily cause air blockage.