Hot Enough for You? Your Electric Fan May Not Be Helping

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This might seem counterintuitive if you’ve ever cooled yourself down by the stiff breeze of an electric fan, but a new review published in the Cochrane Library suggests that there’s no good evidence that fans help during a heatwave.

Unlike air conditioning, electric fans don’t actually cool the air, but bring in cooler air from outside if placed near a window. That backfires, however, when air temperatures rise over 95°F — using an electric fan when it’s that hot can actually increase your body’s heat stress by blowing air that is warmer than the ideal body temperature over your skin. You may still feel a cooling sensation as the fan’s breeze evaporates your sweat, but increases in hot-air circulation and sweat evaporation can actually speed heat-related illness, such as heat exhaustion.

“An increase [in] sweating can cause dehydration and electrolyte imbalances. If these fluids and electrolytes are not replaced quickly enough, there is a possibility [that fans] may do more harm than good,” say the authors of the review.

These health issues are particularly worrisome for high risk individuals, such as older people and babies, who are more vulnerable to extremes in temperature in part because they are less likely to recognize symptoms of excessive heat exposure. Older people are also more likely to have underlying medical conditions like heart disease that can be exacerbated by hot weather.

(SPECIAL: Beat The Heat: 7 Hot Weather Survival Tips)

The new review paper has relevance for public-health experts who are working to keep people cool this summer — and beyond. It’s hot around the globe right now, and according to the Intergovernmental Panel on Climate Change, we can look forward to more heatwaves worldwide, thanks to global warming. Increasingly, countries are developing official plans for keeping their citizens from overheating, and many of these plans include recommending the use of electric fans. Same goes for organizers, restaurants and other establishments in London who are preparing for the Olympic Games.

“It is important to know about the potential benefits and harms of electric fans when choosing whether to use one. This is true if you are simply making a decision about your own use of a fan, but it also applies to broader public health decisions, such as whether to give electric fans to groups of people during a heatwave,” said review author Dr. Saurabh Gupta, a consultant in public health at Hertfordshire Community NHS Trust, in the U.K., in a statement.

For its part, the U.S. Centers for Disease Control and Prevention (CDC) recommends electric fan use only when temperatures are below the 90s. Otherwise, people should turn on the air conditioning to cool down. If you don’t have A/C, the CDC recommends taking a cool shower or bath, refraining from turning on the stove or oven to maintain a cooler temperature, and calling a local health department to see if there are any heat-relief shelters in your area.

(MORE: Now Do You Believe in Global Warming?)

The authors of the Cochrane paper based their findings on published and unpublished studies that compared people who used fans with those who didn’t during a heatwave. They also consulted health experts with keen knowledge of how heatwaves influence health. The researchers couldn’t find any gold-standard randomized trials examining the issue, but they did dig up some retrospective, observational studies on electric-fan use. The findings were highly varied: some concluded that when people used fans during a heatwave, they were less likely to suffer heat illnesses or heat-related death, but other studies found no such benefit.

In a podcast discussing the study, the authors conclude:

Our review does not support or refute the use of electric fans during a heatwave and people making decisions about them should consider the current state of the evidence base. They might also wish to make themselves aware of local policy or guidelines when making a choice about whether or not to use or supply electric fans.

“This is an incredibly important area of research for people seeking relief and a strategy to prevent negative effects of heat, including hospitalization and death,” says Dr. Kay Dickersin, director of the U.S. Cochrane Center at Johns Hopkins University, who studies heatwaves but was not involved in the current review.

MORE: Why Are Parents Less Likely to Take Little Girls Outside to Play?


So basically the moral of the story is use common sense.

One thing people fail to understand about using fans in windows though is that to make the most of it you want your fan that's pulling air in to pull in the coolest air possible, so from a window or area of the home that's shaded.  If you're going to put a fan in front of a window that's hot it's actually better to have the fan facing out.  This is why most fans designed to be put in windows have a forward and reverse or intake and exhaust setting.   The entire point is to create a current in the home where cool air is being moved into warmer areas... not to just indiscriminately push air around in all directions.

Sandeep Singh
Sandeep Singh

In short, don't use a fan to blow hot air on yourself. Do we really need an article to tell us that? I thought it was common sense. 


You can take my fan when you pry it from my hot, dead hands.


Deb's tips for Life Without an Air Conditioner.

I don't have one, just cannot STAND the stink of air through one of the things, so have learned a few nifty tricks that work very well even in the hottest weather.

Take an over-sized lightweight cotton teeshirt and soak it and give it a good wringing *then* slip it on and sit in front of a fan..

If I've gotten a sunburn and am hot and trying to sleep, I do the wet teeshirt trick and have the fan move air across the bed and it really does give enough relief to get to sleep. To keep from peeling, wash the sunburned area with cool water then put on straight, plain, cold cream and slip on the wet shirt. The cold cream and the dampness from the shirt keep just enough moisture in the skin to help it stay in place instead of coming off too soon.

At almost any temperature the water in the shirt will evaporate if it's in front of moving air and that cools the body just as well. It's better actually that you end up not sweating out as much, and you keep re-soaking the shirt as you need.

Of course when it is super-hot for the love of God, don't bring in hot outside air!

The best thing to do is run the fans overnight to pull in the coolest early-morning air, then by 9 a.m. you should have the shades drawn on the sunny side of the house and circulate the cool air around inside - if you have a tree next to a home, use the window nearest it to pull in air - trees keep air moist under them as it is in shade and will be a few degrees cooler. Not much, but enough to help if it is super-hot. (That is the window you want to pull air in through in the evening as again, the tree holds moisture and an evaporation - cooling - cycle around it.)

Also, a wallpaper water tray on the floor in front of a fan, with the air blowing across the top of the full tray makes a bit of evaporation - which is cooling - and that helps a room. You'll be amazed how fast that empties in really hot weather.

Spray bottles that you can mist yourself with - wonderful while in front of a fan - are also REALLY nice. 

As always, drink lots of water. I got bit with heat exhaustion while out and about last weekend and it was miserable.. Buuuu..


Clearly the author of this article has some personal issue with electric fan use. I feel that there is a slant in this article that seems to suggest fans are harmful. Please accurately report the findings of the review-- the bottom line is that the evidence does not resolve the issue (i.e. we don't know if fans help or harm!). It is the typical Cochrane review with insufficient evidence to support a clear conclusion. The evidence does not support use of fans but it does not refute it either so you can't go around essentially stating that fans are harmful and do not provide adequate relief from heat.