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Is it Safe to use an Electric fan for Cooling?
Ignoring Betteridge's Law of Headlines, it appears that different guidelines have been promulgated regarding when it is, and is not, safe and effective to use a fan to cool off.
The safety and effectiveness of electric fans in heatwaves depend on the climate and basing public health advice on common weather metrics could be misleading, according to a new study from the University of Sydney.
[...] The results, published today in Annals of Internal Medicine, show that in a hot, humid condition with a heat index of 56 °C (133°F) fans lowered core temperature and cardiovascular strain, and improved thermal comfort.
However, fans were detrimental for all measures in very hot, dry conditions despite a lower heat index of 46 °C (115°F).
Heat index is a commonly used weather metric that expresses both air temperature and relative humidity. It was designed to help convey how hot weather conditions feel to the average person.
The United States Environmental Protection Agency (USEPA) states that fan use above a heat index of 37.2°C (99°F) "actually increases the heat stress the body must respond to."
[...] "Our results suggest that under environmental conditions that represent the vast majority of peak heatwaves in the United States and Europe fans should be recommended and the guidelines issued by most public health authorities are unnecessarily conservative," said Associate Professor Jay.
"It is only when the air temperature is very high and humidity is very low that fans are detrimental, which can be seen in arid conditions such as Phoenix or Las Vegas in the US, or Adelaide in South Australia."
Journal Reference:
Nathan B. Morris, Timothy English, Lily Hospers, Anthony Capon, Ollie Jay. The Effects of Electric Fan Use Under Differing Resting Heat Index Conditions: A Clinical Trial. Annals of Internal Medicine, 2019; DOI: 10.7326/M19-0512
(Score: 1, Informative) by Anonymous Coward on Tuesday August 06 2019, @05:30AM (6 children)
I left a fan on on this super hot day, and it killed me.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @05:50AM
Good to have this point of data. Now I can mark this commit in my "git bisect" to figure out which one gave SN the ability to speak to the dead.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @02:06PM
You should've used a gasoline powered fan.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @03:40PM (2 children)
You do realize it happens right? I believe the probability of death is low, but it might cause severe dehydration which is bad enough. Got a problem with health recommendations??
(Score: 2) by Freeman on Tuesday August 06 2019, @04:21PM (1 child)
Myth: Plausible (Just don't use one to blast yourself with hot air!) I wouldn't be surprised, if this is commonly misunderstood. Though, I would assume, people would be using swamp coolers, instead of just fans.
https://en.wikipedia.org/wiki/Fan_death [wikipedia.org]
Myth: Debunked
Also, from the same wikipedia entry:
Myth: Debunked
Yeah, that's not how things work, unless the ambient temperature is greatly reduced. At which point the fan's contribution to the harm done is negligible anyway.
Joshua 1:9 "Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee"
(Score: 1, Touché) by Anonymous Coward on Tuesday August 06 2019, @07:11PM
Are you gonna trust some random internet website (wikipedia) or me who's already god damn dead?!
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @08:59PM
Now you're in a good position to test a fan in Hell.
(Score: 4, Insightful) by Coward, Anonymous on Tuesday August 06 2019, @05:57AM (7 children)
Just stop using Heat Index. Temperature and humidity are totally different things. I guess they wanted a single quantity that corresponds to human heat stress. But as TFA says, human reaction also depends on airspeed, which is different for everyone.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @06:25AM
Heat Index (R), made with our proprietry formula.
Looks like you do not have a copyright license to reference our product and so your post will be deleted.
(Score: 3, Funny) by inertnet on Tuesday August 06 2019, @08:59AM
I'm not a fan either.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @11:20AM (3 children)
Instead, use the ASHRAE psychrometric chart. Originally developed as a design aid for air conditioning and heating applications, it's a well established method of determining "comfort", https://www.ashrae.org/technical-resources/bookstore/psychrometrics [ashrae.org] A search shows many other sites with similar information.
(Score: 2) by Osamabobama on Tuesday August 06 2019, @06:44PM (2 children)
That chart is one of my favorites in the field of thermodynamics. It slices the data about five different ways: wet bulb, dry bulb, dew point, absolute humidity, relative humidity, enthalpy... Where do you find the 'comfort' zone?
I mean, I can look at a point on the chart and decide whether I'd like to live there, but is there something beyond that?
Appended to the end of comments you post. Max: 120 chars.
(Score: 0) by Anonymous Coward on Wednesday August 07 2019, @03:07AM (1 child)
I've forgotten just about everything I learned back in my heat and vent class (1976, and only used it a few times back then...)
This looks like a nice explanation, with a slightly simplified/linearized chart:
https://www.ohio.edu/mechanical/thermo/Applied/Chapt.7_11/Chapter10b.html [ohio.edu]
Search for "comfort zone". The last ~1/4 of that page has several worked problems.
(Score: 0) by Anonymous Coward on Wednesday August 07 2019, @03:18AM
One more thing that is included in complete comfort zone calculations is the air velocity. Even a very slight amount of air movement can move a person into (or out of) the comfort zone.
Thermal comfort is one of those problems that is just a bit too complex, until you've had some explanation, and perhaps a few pre-reqs in advance. Thus there are constant attempts to simplify this complex problem to one number ("heat index", "real feel temp", etc.) for most people that are never going to understand the full Psychrometric Chart.
Another response is to focus on just one aspect of the problem (for example, there is a nearby post that tries to simplify the complex problem by, "use Dew Point"). This may work in some subset of the problem space, but won't work globally.
(Score: 2) by AthanasiusKircher on Tuesday August 06 2019, @06:39PM
Or, even simpler, look at dew point [wikipedia.org].
The problem with just giving humidity measurements (almost always relative humidity) is that they are about as meaningless as temperature is by itself when it comes to estimating human comfort levels. 90% humidity when it's 45 degrees F may feel a bit "sticky" or "damp," but it isn't a lot more uncomfortable than much less relative humidity at that temperature. Whereas 90% humidity at 100 degrees F may be deadly to people with health problems or the elderly, where they might be okay (if not quite comfortable) with much drier air at that temperature.
If you don't like the heat index, try dew point, because that's basically a measure of absolute humidity, and that is often most relevant to human comfort in the "warm to hot" temperature range. Dew point is basically the main number I look at in the summer if I want to know whether I'm going to sweat outside. If the dew point is 50F, I'm happy. If the dew point is over 70F, I'll be soaked even if the temp is only 75F. If the dew point isn't going below 65F at night, look forward to muggy days ahead. If the dew point is dropping back down into the 50s at night, you'll have a chance to dry out. The actual overnight low is less important here than whether moisture is staying in the air, and dew point tells you that.
The problem with just stating temperature and (relative) humidity is that those combinations are still very difficult to interpret for most people, since the effect of humidity is different at every temperature (hence the heat index as an attempt to simplify this problem). If you actually are trying to assess human comfort, I'd tend to look at temp and dew point instead for a rough approximation. And dew point is easier for most people to understand than the units of absolute humidity (usually grams water per kilogram air or something similar) -- a dew point temperature that's close to the temp outside means the air will be "sticky" -- if there's a big gap between them, it won't be. Pretty intuitive.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @06:08AM (1 child)
fan death on Wikipedia [wikipedia.org]
(Score: 2) by FatPhil on Tuesday August 06 2019, @12:55PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Informative) by Revek on Tuesday August 06 2019, @06:18AM
Its 70% now and 55% in my house with the ac running most of the time. Most people use fans outside here to keep mosquito away. Luckily the little pests can't fly when there is a slight breeze and they are effective at keeping them away from you.
This page was generated by a Swarm of Roaming Elephants
(Score: 2, Funny) by Anonymous Coward on Tuesday August 06 2019, @06:34AM (1 child)
You see, sleep is the brother of death. When you are asleep, the connection of the soul to the body is weakened, and your soul can actually emerge from your mouth to look around. Now if a fan, an oscillating fan, is in the room, it can swing around unbeknownst to your soul, and blow it off your lips, much like getting the wind knocked out of you in sports. And of course, if you do not get back your wind, your breath, your pneuma and anima, you are dead. So sleep in your sweat, dudes and dudettes. Korea already knows this.
(Score: 2) by VLM on Tuesday August 06 2019, @12:34PM
Yes my Korean coworker and I used to discuss this. Fan death is a popular belief over there.
Seems to mostly be asceticism to me; he sees it as old wives tale or fable kinda thing.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @06:47AM
Thomas Merton, Trappist monk and author of the "Seven Storey Mountain" [wikipedia.org], was killed by an ungrounded fan in a shower in Thailand. God's way of calling the better amoung us home, no doubt.
(Score: 3, Interesting) by slinches on Tuesday August 06 2019, @06:47AM
I live in Phoenix and while it's true that there's a point where breeze or a fan will actually make you hotter, it only occurs very near the all time record highs. The break even point is somewhere between 115-120F depending on humidity here. Above that point cooling from evaporation of sweat is already maximized and the increased convection from the higher airflow raises your body temperature. Below that point, there effectiveness of perspiration cooling is enhanced by more rapid evaporation. The reason they stated 99F as a cutoff is because that's above human body temperature. So if you don't sweat due to dehydration or a medical condition, then that's good advice. For the rest of us, feel free to use a fan above that. Just be sure to hydrate well if you are out in a hot and dry climate, whether you use a fan or not. Oh and if a fan makes you feel hotter, turn it off no matter if it's dry or humid.
(Score: 1, Interesting) by Anonymous Coward on Tuesday August 06 2019, @08:36AM (6 children)
Isn't the obvious solution a swamp cooler whenever you have high temperature and low humidity? It's a match made in heaven. If you're feeling cheap, dip a ratty t-shirt in water, wring it out and drape it over the fan. Problem solved.
If you happen to live in an area where high temperature entails high humidity the only solution is air conditioning, with all the expense and complication that involves.
(Score: 4, Interesting) by VLM on Tuesday August 06 2019, @12:42PM (5 children)
That's exactly what makes the story so weird from an engineering standpoint. Basically sweaty clothes and body are a really short range swamp cooler.
In a gentle breeze just fast enough to displace evaporated water, sweaty skin can't be above the dew point, which is low in a desert. Doesn't matter if you have 0.1 mm of sweat on your skin or 3 mm of sweat on your skin and the air speed doesn't matter until you get to convection oven speeds where its like a heat gun.
My guess is there's a bad human behavior feedback loop where a gentle breeze would cool people off to near hypothermic levels in low humidity, but "its hot as hell so turn the fan up all the way and stand in front of it" results in a heat gun or convection oven like effect where they roast themselves "because its hot" whereas a wise engineer would lower the fan speed and increase the distance to the most gentle breeze keeping up with sweat evaporation resulting in being comfy, or at most a little soggy.
Kinda like the feedback loop where its very easy to die of hypothermia in the winter by exercising (snow shoveling?) too hard resulting in a puddle of sweat that freezes, and the average moron or new resident doesn't understand that the fastest path to freezing to death is working too hard in cold weather. So you get sweaty, oh shit I'm freezing work harder, and increase until frostbite, hypothermia, or heart attack. Meanwhile someone who takes their time working outdoors at a sane slow constant pace can find even the worst snow shoveling below zero to be fairly comfortable with the right clothing.
(Score: 2) by DannyB on Tuesday August 06 2019, @02:24PM (1 child)
What about using a fan that sprays a fine mist?
If you eat an entire cake without cutting it, you technically only had one piece.
(Score: 2) by HiThere on Tuesday August 06 2019, @05:14PM
If the humidity is high enough, that doesn't help....unless, possibly, the mist is made from ice water.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 5, Informative) by slinches on Tuesday August 06 2019, @02:52PM (2 children)
In extreme hot/dry conditions (e.g. 120F and 5% humidity), you can't perspire fast enough to keep up with evaporation. Your skin and clothes are completely dry whether there's any wind or not. I have been in these conditions and no one will turn on a fan if they have a choice. Wind feels like you're in a convection oven and can make your skin burn painfully. The senses work well for detecting dangerous conditions like that and will tell you to get somewhere cooler.
What's usually more dangerous are less extreme conditions. At 105F and very low humidity, it can feel quite comfortable and you won't even realize that you're sweating. People die from exposure in these conditions more often than on the hottest days of the year because they don't feel like it's that hot and go out for a hike in the desert with far too little water. It can take only a couple of hours without water to get severe heat exhaustion and you can die of heat stroke in one afternoon without a way to stay hydrated and keep cool.
(Score: 2) by hendrikboom on Tuesday August 06 2019, @07:36PM (1 child)
When you can't sweat fast enough, perhaps take sponge baths, make yourself we all over, and let yourself dry be evaporation>
(Score: 2) by slinches on Tuesday August 06 2019, @08:15PM
Yep. Putting a wet cloth around your neck is good, as are pools, misters and swamp coolers. Anything that supplements evaporative cooling is highly effective.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @10:22AM
No climate change, nothing to see here...and don't use your fans to cool off!
(Score: 2) by DavePolaschek on Tuesday August 06 2019, @11:33AM
Here I was expecting something saying that the carbon dioxide released to make the electricity... blah blah blah. But at least it would be new information.
Instead, I find that the article says, if the air is too hot, a fan works like a hair dryer or a convection oven. Not exactly news, that.
I want a moderate articles. -1 Clickbait.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @12:10PM
Sorry, but isn't it well known that fans cool better when it is humid?
(Score: 1, Informative) by Anonymous Coward on Tuesday August 06 2019, @07:28PM (2 children)
Run cold tap water over your wrists.
It takes less than a minute of cool water next to large blood vessels before you feel your face cool off.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @08:00PM
I've always preferred soaking my feet.
(Score: 0) by Anonymous Coward on Tuesday August 06 2019, @09:22PM
"from a Lousiana native"
Didn't occur to you to move up north (cooler) and west (drier), eh? That's why you are stuck in LA.
(Score: 0) by Anonymous Coward on Wednesday August 07 2019, @03:06AM (1 child)
Turn your house into a cave and block out the solar radiation. You need to move the air around still and the fan will help that. But cutting solar radiation through windows helps tremendously. Also, fans definitely help move air in attics where most hot air accumulates and radiates into your home. So if the fan is not working on you...put it on full blast in your attic.
(Score: 0) by Anonymous Coward on Wednesday August 07 2019, @03:24AM
For the hottest part of the summer, I tape up sheets of aluminized Mylar (plastic mirror) on inside of the windows facing the sun... it would work even better if I could put the mirrors on the outside, but then they would probably blow away.