A question over on DIY.SE about sizing a range hood exhaust got me thinking about whether I should be running the exhaust fan every time I cook. Is it supposed to be more of a proactive or reactive piece of equipment - i.e., should I only turn it on in response to a problem, or always turn it on before cooking anything (or any specific types of cooking)?

I only run it now when it gets noticeably smoky around the stove, which is usually when I'm cooking in my cast iron skillet. I mainly turn it on in an effort to avoid setting off the smoke detector (which sometimes works and sometimes doesn't).

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As you call it an "exhaust" I assume it's an extracting type rather than a filtered recirculating type.

It's a good idea to run it:

  • Whenever you're frying (it handles grease droplets in the air as well as smoke)
  • When you have the potential to produce smoke (so not generally when cooking in the oven, but sometimes, if things might drip or spatter).
  • When you're cooking something that might make the house smell for longer than you'd like.

Generally speaking you should use it in anticipation of smoke/grease/odours, though using it reactively for toaster smoke is also a good idea.

Boiling is another matter. If the house gets damp, running the fan when boiling will reduce that (as of course will boiling with a lid on). Some houses end up rather dry (e.g. with forced air heating), in which case it's probably not worth turning the fan on. In summer I'd rather open the window.

It's worth thinking of where the air comes in to replace that sucked out by the fan. I have a rather open plan living area, and open a little ventilation at the far end from the kitchen, so the fresh air comes through the sitting and dining areas to the kitchen. But here in the UK we have "trickle vents" over many windows that are designed to deliver fresh air without you feeling a draught unless you're very close.

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    What, if anything, changes for a recirculating type of vent fan?
    – mmathis
    Feb 23, 2018 at 21:33
  • There's no point running a recirculating fan when simply boiling -- it returns the steam to the room. And you have to pay more attention to the filters as the odour filter is additional. Also there's no need to consider where the replacement air comes from
    – Chris H
    Feb 23, 2018 at 22:01
  • @ChrisH Some if not much of the steam would condense on filters or other surfaces.
    – paparazzo
    Feb 24, 2018 at 0:50
  • @paparazzi I suspect not much, though I can't be bothered to calculate based on heat capacities. That steam would still end up in the room, just a bit delayed, as the filters would have to dry out or the hood would fill with water.
    – Chris H
    Feb 24, 2018 at 7:22
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    @ChrisH Don't be bothered.
    – paparazzo
    Feb 24, 2018 at 12:36

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