YSK that your above-range microwave likely contains a charcoal air filter at the top where the fan blows out recirculating air when the fan is on. Replacing this inexpensive filter can remove cooking odors from your kitchen.
from /r/YouShouldKnow
YSK，您的微波炉上面很可能在顶部有一个木炭空气过滤器，当风扇打开时，风扇会将循环空气吹出。更换这种廉价的过滤器可以去除厨房中的烹饪气味。