Thank you for that quote. It backs up what I said long ago when this first cropped up. High temperatures, high humidity, and a fan for cooling can be a bad combination. Evaporation can only cool so much, and the higher the humidity is, the less effective that cooling becomes. At some point, it stops being cooling and starts being a low temperature convection oven - essentially “baking” you by dumping even more heat into your body, albeit at a very low rate. Dehydration and heat stroke can result, possibly leading to death.
I remember reading newspaper articles in the 1970’s during heat waves that included mention of people killed by heat stroke from fans.
High temperature and high humidity environments can indeed potentially be fatal.
But why would a fan make such environments more dangerous?
I can only see it acting like a convection oven if the temperature is greater than human body temperature, and the humidity is higher than the air immediately around a normally sweating person. In which case you’d be screwed anyway, even if the air was perfectly still.
Also, these kinds of conditions are far less likely at night.
I think the difference is that hot air blowing directly at you continuously evaporates sweat but immediately replaces the cooler air from that evaporation with hot air again. The constant replacement of the cool air around you causes faster dehydration and a faster temperature increase than would be the case without the fan. The motor of the fan makes at least some heat too, so in a small enough room that alone would make a bad situation worse with no outside air exchange.
I…think that makes sense.
The only issue I have is that I don’t think evaporation directly cools the air around you – it cools the skin, which may then in turn cause the air around you to cool.
When I’m running the still and moving air simulations in my brain, it’s getting complex, but I assume that if the FDA are saying it can be dangerous they’ve done the math / gathered empirical data.
Then I’d say you’ve never been exposed to a heat wave with high humidity and high temps, with an inversion layer to keep the nights hot. Nothing much sucks worse than a long, hot, muggy day followed by a long, hot, muggy night.
What happens is that in the conditions we are talking about, sweating doesn’t provide really any cooling at all. You body is basically absorbing heat from the air, thereby cooling the air a bit. Now start blowing the air around, and your body will have more heat to absorb - bake-o-rama. In those conditions, you will get heat stroke anyway. The fan makes it happen enough faster that you might not realize you are in trouble (especially if you are sleeping.) Factor in that people assume the fan is cooling the air and will stick around in the heat longer, and you’ve got the cause of the problem.
You first describe a situation where sweating doesn’t provide any cooling – this implies an extremely high humidity. You then go on to add that the body is a net heat sink in this situation – meaning, indirectly, that the ambient temperature is hotter than human internal body temperature.
Well, the situation you describe is fatal to humans.
Still air, moving air, humans can’t survive prolonged exposure to a wet-bulb temperature greater than body temperature.
It’s a red-herring to talk about fans in such an extreme situation.
I wonder what believers in fan death would make of studies that show that fans in babies’ rooms reduce the risk of SIDS by more than 70%. Is fan death only an adult problem?
As someone who has experienced those conditions, I’ll just say that, in those circumstances, it is obvious that a fan blowing more hot air on you is worse than having no fan at all. Your body just knows, almost instantly.
When I’ve been in those circumstances, it seems like it’s almost instinctual to seek out any available body of water and immerse yourself in it.
I think the message (at least from the EPA) is more like ‘open up a window or get out of the house. Don’t just turn on a fan and go to sleep thinking it is going to keep you cooler than room temperature’. If someone were awake in these circumstances they could keep guzzling water and sweating but asleep it could make the situation more dangerous than it already is.
That’s very true. Also, one thing I forgot is that our thermoregulation doesn’t work so well while we are asleep. So even if it’s a little cooler at night than during the day, it may still be a high risk period for heat stroke (although experience suggests that if you get very hot or cold while asleep you tend to wake up).
It is very much a meme–a parcel of cultural information, transmissible from one person to another. That it is widespread and persistent in Korea confirms that it is a successful meme, well-adapted to that environment. The vast majority of memes have unknown origins.
Yes, I was just thinking that my Grandparents and born-in-Korea mother never mentioned it. Even when we were sleeping with fans.
We Always slept with the fans on in Lae, PNG. But the windows were open too. My wife would never sleep with a fan (or air-conditioner) blowing on her. She doesn’t think she is going to die, just that she will wish she had.
Of course, trying to sleep with a belief system like that is never going to work, so I’ve never been able to demonstrate to her how much I LOVE sleeping with a fan on.
Interesting thread, too bad I missed it the first go around.
Taiwan is very much into cold not being good for people. My wife sort of freaks out when I give our small! kids ice! I’ve had people here tell me to not drink too much ice water.
