Why do fans cool you off when it is hot?

Fans By the Autowitch, on FlickrIt’s a hot summers day. You are slaving away at work in the office, sweat dripping off your forehead, counting down the time until you will be released. You have no air conditioning, the windows are open and you’ve stripped off every piece of clothing that you can while maintaining your decency. As a last resort, you plug in and turn on every fan available to you, making sure they all face your desk (and ignoring everybody else’s needs!). So why is it, then, that a fan will cool you down? Surely it is just blasting hot air around the already very hot room?

Well, it will probably surprise you to learn that fans don’t actually cool the room at all – they heat it! The spinning motor, moving parts and electrical current all produce heat. And yet, managers and deputies will always prefer you to plug a fan in (and continue working, may I add) rather than going outside to catch a breather – how short-sighted!

So while fans heat the room slightly, they cool you down because they create a wind-chill effect. This is a meteorological term that is used to explain how moving air can actually make us feel colder than the temperature recorded on the thermometer. By fanning air onto your skin, it blows away the warm layer of air above it (which has been heated by your body). Additionally, any breeze will cause any sweat and moisture on the skin to evaporate more quickly (just like how your washing will dry faster when hung out on a windy day). For whenever a liquid evaporates, it takes heat from its surroundings – you can feel this cooling effect whenever you are wet, but will notice it more when you spray on some perfume (the alcohol in the cologne evaporates much faster than water, making the cooling more obvious). The cooling effect of evaporation is also why sweating is your body’s built-in cooling system.

So as the temperature increases, the sweat glands in our skin (we have millions of them!) become activated, producing salty water that flows out of your pores. The more you sweat, the more evaporative cooling takes place and the more the fan will cool you off. But remember that sweating can result in nasty body odour problems which could make office working quite unpleasant. My suggestion? Spray on some perfume before you get too hot. A cool skin and a nice smell: win-win!

Answer By Chloe Westley


Image Source: Fans By the Autowitch, on Flickr

Article by Chloe Westley

September 18, 2014

Based in Manchester, UK, Chloe spends most of her time getting up close and personal with a zippy bit of kit called a Raman spectrometer. In between doing some high-brow research as part of a PhD, she follows tennis, cricket and Man United (unfortunately) and loves watching Suits, The Big Bang theory and Breaking Bad (obviously!).

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