A hot day, a fan provides little benefit when the temperature exceeds 35°C
science.org
science.org
I don't know quite how to put this, but are they idiots? I don't quite mean that, but at the very least there's something weird going on. I double down on this as they double down on their recommendation at the end of the article.
Go to places like India, and see how people use fans, in the humid places like Kolkata and the dry places like Hyderabad. Fans obviously provide great relief at far higher temperatures than their 90°F. The very idea of suggesting not to use fans from such a low temperature is, to me who grew up in Melbourne, Australia and now lives in Hyderabad: ludicrous.
Even when they talk about "people who are less able to cope with heat", it sounds like they may be giving advice very harmful to normal people, for the possible but highly contested safety of a few.
——
When talking about ineffectiveness of fans in high temperature low humidity (which is Hyderabad summer to a tee—it barely gets below CDC's 90°F, and is very dry), the details mentioned make me sceptical of the entire approach of the studies. I know each time I've come to India, it's taken me well over a week to adjust to the temperature. (I still sweat more than most Indians do, but not as much as a day or two after I come.) And hydration is a rather important factor too, likely not accounted for adequately. We're talking definite heat stress circumstances, you can't expect to get accurate results from an unacclimated body.
Yes, I am a layman casting doubt on the work of experts without investigating carefully. I imagine they've been at least somewhat careful about these things, none of these people will be idiots. It's probably not all as bad as the vibes I'm getting. Do treat my scepticism with scepticism of your own.
It’s the COVID garbage all over again. They think the public are absolute drooling morons who cannot be trusted with any nuance, and they bake this prejudice into their recommendations.
Good lord, we are never going to be able to rebuild trust in our institutions if they haven’t learned any lessons over the last 5 years.
I don't know where you've been the past couple years, but I think that's a fairly safe assumption.
tldr: America fast food restaurants don't offer 1/3rd pound burgers because the general public knows that 3 < 4
"They" aren't aliens. "They" come from that same public, and are as much drooling morons as the rest of the public (what i frequently remind to the Russians who whine about the Russian government).
>to rebuild trust in our institutions
will see how appointment of Kennedy Jr. as the health services tzar would work here :)
Popular thinking among the Russian opposition is that the way Western societies reacted to Covid demonstrated to Putin the loss by those societies and by their institutions of the ability to act reasonably. And the inept reaction to the war in Ukraine seems to confirm that.
Fans are an absolute necessity. Classrooms without fans mean kids sleeping in class due to overheating. Being at home without a fan is an absurd notion (unless you have AC, of course).
Go out in a hot day when the air is mostly still, and feel the relief every time the smallest breeze flows by.
Skin has natural heatsinks, especially sweat. Blow air onto them and their efficiency multiplies. We should all know this - we put big fans atop CPU/GPU heatsinks for a reason.
He was right technically of course - 30 students waving something will probably heat up a windowless classroom a degree or two - but it still felt much better to have the air movement.
The room I'm in now does get hot, and a fan pointing inward with one closed window doesn't help me feel more comfortable, but if I open 2 windows and have a fan pointing outward to create a current, it's great. Fans can blow hot air in an enclosed space and be unhelpful.
The article did mention some studies spritzed participants with water, but didn't seem like they tested it across all possible conditions. Seems like spritzing yourself with water even in a dry environment would make a fan still a benefit at higher temps, given the proposed explanations in the article.
If the American population had to face hot and humid climate like that of North India, there will be an uproar and some big central solution pushed very quickly.
It's between fan and no fan. The supposed reason is the additional heating via convection that takes place.
I 100% agree with your sentiment, fans work even at 110F.
>I don't know quite how to put this, but are they idiots?
I can't believe they said that. They need to move anywhere in the US Southern region. 32.2C is a cool day reprieve in a Southern summer and fans are a necessity.
https://baltimoreaircoil.com/evaporative-cooling#:~:text=As%....
anyway.
using the magic of google I found:
>Use fans, but only if indoor temperatures are less than 90°F. In temperatures above 90°F, a fan can increase body temperature.
https://www.cdc.gov/heat-health/about/index.html
further searches led to:
>under the hot and dry conditions, however, the fans increased body temperature, the strain on the heart, and thermal discomfort. In other words, the fans worked better at higher heat index temperatures.
>There’s a physiological explanation: When air temperature soars above skin temperature, then the exchange of air between the body and the air switches; rather than dissipating away from the body, heat from the hotter air starts to flow into the body.
https://time.com/5644737/fans-can-make-you-hotter/
which cites this study:
Nathan B. Morris, Timothy English, Lily Hospers, et al. The Effects of Electric Fan Use Under Differing Resting Heat Index Conditions: A Clinical Trial. Ann Intern Med.2019;171:675-677. doi:10.7326/M19-0512
Searching the doi on google scholar reveals the stuyd, published in 2019, has 75 citations so far
> New research from two different groups of thermal physiologists favors the higher temperature limits, especially in humid weather. But the groups don’t agree on a single temperature threshold. One study, published on 6 November in The New England Journal of Medicine (NEJM), reports that fans can relieve stress on the heart in elderly people in humid conditions at 38°C. The other, published on 17 October in JAMA, concluded there was little additional benefit from using a fan above 35°C.
The NEJM article is pay-to-read. The JAMA article took older adults, had them sit in a room at 36C, for 8 hours, getting very occasional light exercise and tested three different air movement speeds. The body temperature of the subjects was 38C, independent of fan speed, from which IMO one can conclude approximately nothing other than that the subjects' bodies were warmer than ideal under those conditions.
In my personal experience, the effect of air movement and body movement under conditions like this is dramatic. "Resting" (as the study had the subjects do) in the daytime (as the subjects did) is, for me, not so pleasant. Add a fan, and it's less unpleasant. Riding a bike can be very pleasant as long as there's plenty to drink. But I suspect that my rectal temperature would be more or less independent of any of this.
This is a real problem. A lot of people are found dead sitting in their closed apartments in front of a fan, thinking it would cool them off during a heat wave.
One might imagine the solution to that problem is, 'don't use fans', but that would result in people dying from heat illnesses. They need to find a threshold that minimizes those very bad outcomes.
The chart in this wiki article is really good at showing the various effects.
More cooling but (paradoxically) lower water consumption.
Summary: https://www.youtube.com/watch?v=sJl-NIgGDL8#t=89
Long-form (chart @29:30): https://www.youtube.com/watch?v=aVgB557bz0I
I agree. The article mentions all of this... when it gets that hot, especially with US-Midwest humidity levels, you need evaporative cooling with "just a fan". The phase change absorbs energy and can provide relief to higher temps.
https://en.wikipedia.org/wiki/Evaporative_cooler
which gives excellent cooling with small amounts of water and electricity. Good luck trying that in New York!
Is that a typo or a real term?
All moving air does is increase the rate of the heat transfer from the higher temp substance to the lower temp one. If the air outside is hotter than your body temperature then a fan will be heating you UP not cooling you DOWN.
Without electricity or chemical reactions the only way to stay cool in high heats is to use evaporative effects. Evaporation is endothermic (takes in heat) and actually cools down the thing being evaporated off of. So you can basically soak your shirt and as it evaporates it cools you down. There are things called 'evaporative vests' which can cool you off for hours.
This is why fans are found to be generally effective to 104 degrees. https://time.com/5644737/fans-can-make-you-hotter/
The OP goes through a lot of evidence saying the threshold is lower.
I’d replace top with something like: A fan isn’t directly helpful, unlike an AC it’s not going to cool an empty closed room. However, it can make a wider range of temperatures and humidity levels comfortable through aiding evaporation or bringing in cooler air when possible.
This is why as the article mentions a fan alone can be worse than doing nothing in sufficiently hot and dry air. People only sweat so fast so at some point without supplemental moisture the fan acts like a convection oven simply warming people faster. This can be offset by adding supplemental moisture via a 'evaporative vests' or mister the maximum temperature increases.
This and other reasons mean health organizations are concerned with finding and communicating the maximum temperature fans are still useful.
Or like, sweat? Which is something people who aren't dehydrated tend to do at or above 95F (35C).
...and this is what makes the actual difference and matters much more than the temperature itself.
> People live in hot climates year round without feeling miserable all the time.
Not this person, nor my sons (born here) or siblings. Heat makes us all sick.
Florida has 6 or 8 actual seasons and none of them are Fall, Spring or Winter.
Over 30y, I can give all possible answers to that question. I was 15y in scouting leadership. During June-Aug, I would be outdoors for weeks at a time. What I got used to was feeling sick every day.
That said, early heat stroke symptoms get old after a decade or three. Now I go outside after sunset.
This flips with supplemental water which once again makes faster fan speeds useful up to significantly higher temperatures. Obviously there’s another limit as a mister alone can’t lower a rocket engine exhaust to be comfortable.
Net result a lot of seemingly contradictory recommendations shown in the article.
And you don't need to soak your shirt, you just need to sweat which happens automatically in most people.
So even with hotter air, the fan can be cooling you DOWN.
"... results in dry conditions starkly illustrated the dangers of misusing fans. The scientists stopped the experiments after testing just 14 people because their cardiac stress went through the roof as the fan blew hot air on them. Nearly half the participants couldn’t stay in the test room for 3 hours. The reason for that dramatic response: The air was so dry that any sweat quickly evaporated, resulting in little additional cooling as the fan bathed participants in extremely hot air, Jay says."
Why would faster evaporation result in less cooling? I could make some guesses but I wonder what the reality is.
Possibly, they mean that the evaporation was exhausted quickly and after that, it was just a convection oven.
"The air was so dry that any sweat quickly evaporated, resulting in little additional cooling ..."
Why wouldn't blowing 27C air over your 37C body cool you off? The fan isn't adding 10C to the room temperature (or you need a new fan).
- The HN title is misleading. The real title is "When is it too hot to use a fan?"
- The article explains: "The key point: Above 35°C, humidity matters a lot. In very dry conditions, a fan could be counterproductive, whereas in very humid ones it could continue to help at much higher temperatures." They quote two controlled studies that show the same results so there's no reason to debate this.
It's just a bad title. There's nothing controversial here.