I always use the exhaust fan every time I use the stove or the oven. It does not matter if I'm only boiling pasta, it is second nature. I thought that these fans are used only for getting rid of food odors. Do you know that these keep your counters free of grease and grime? Turn on your exhaust fan every time you cook, this will keep airborne grease away from your counters and appliances. If you wear eyeglasses like me, wear a baseball cap when frying food. These will help keep grease away from your eyeglasses. I know, it sounds weird but hey, it works. :o)