Humid Heat Can Kill Us Much Faster Than We Thought | Hacker News Reader

Humid Heat Can Kill Us Much Faster Than We Thought

nautil.us

85 pointsBrajeshwar36 comments

As posted in a previous thread: https://news.ycombinator.com/item?id=37779158

Quote:

People can survive amazingly hot temperatures, as long as they can sweat - once the wet bulb temp gets far above 31c people are in trouble

/r/collapse (is it unpopular to mention here?) has been discussing wet bulb events for years.

They are occurring with increasing frequency and are very hard to survive without air conditioning or an underground shelter (e.g. cool cave).

But A/C uses large amounts of energy, which not only strains the power grid but also increases CO2 emissions, which causes more extreme wet bulb events...

So what can create dry air? Circulation chimneys and cool caverns were the moisture runs down the wall? I wouldnt want to rely on electricity in a wet-bulb.

I think there are two ways to deal with getting moisture out of the air: 1. desiccants 2. cooling it down past saturation

Desiccants aren't nearly effective enough to dehumidify something like a room. [EDIT: apparently desiccant dehumidifiers are a thing too, although much less common in the home consumer world, so never mind -- disregard this whole comment!]

The answer is #2. Air conditioning units and dehumidifier units, which are essentially the exact same thing except for where the hot air output goes. (AC's send the hot air outdoors; dehumidifiers mix it back with the now-dehumidified cold air.)

> Desiccants aren't nearly effective enough to dehumidify something like a room.

I'm not sure this is true. There's some nasty desiccants that can work effectively, but the trouble is usually in regeneration.

ACs don't send the hot air outside. They transfer the heat outside. They usually recirculate the inside air. But the act of running the inside air across the cooling coils causes water to condenser on the coils and thus dehumidifies the air as well.

If portable A/C units aren't sending the internal air outside, does that mean they're also just circulating outside air as a way to disperse the heat, rather than actually blowing air outside?

Some portable A/C units do send hot air outside, and some don't. The two-hose models AFAIK are the latter type (although the un-insulated hoses are wildly inefficient)

https://youtu.be/_-mBeYC2KGc

And compression

I think electric dehumidifiers are way underused. In a cool wet climate, they're really all you need to stay comfortable down to the 50s. Anywhere you have cold wet air, it can be converted to dry warm air much more efficiently than resistive heating with those things.

Finding ways to cool the air down without electricity might be easier. If nights are still cold you can use thermal mass to get a long-term temperature average (kind of like your caverns). The ancient Persians combined that with evaporation cooling to create fridges. There are also specially engineered paints that radiate heat energy in very specific wavelengths that aren't absorbed by the atmosphere, breaking the equilibrium between absorption and emission of IR and cooling the material by a couple degrees.

Faster than who thought? Feels like every couple months we collectively rediscover "wet bulb temperature".

https://hn.algolia.com/?dateRange=pastYear&page=0&prefix=fal...

If you try going to a dry sauna and then a wet sauna at similar temperatures, you can feel this empirically. I can sit in a dry one for quite a while. Wet, no way...

Saunas are somehow different, because their effect for health is entirely positive. Dry and wet.

Many Finns sit in wet saunas at 70-100C for 10-30 minutes every week.

100C? Where we boil water? ;)

It's not an issue. The dry air insulates fairly well, so your body heats up slowly and you can last a few minutes.

Also in dry air evaporation cooling is very effective, so sweating gets rid of a lot of the heat before it can build up in your body

If you are talking dry air, then how does this apply to wet saunas at 100 degrees?

afaik there are no humid saunas nearly that hot. You'd have a miserable time in there and even breathing would hurt like hell.

Exactly, so here we are talking about dry 100C saunas in replies to someone claiming that Finns sit in wet 100C saunas every week. I find it hard to believe. Humidity makes a massive difference.

Yes. Actually 100C. The sauna i usually go to goes up to 240F (115C). The reason this doesn’t immediately scald you is that air has a tiny fraction of the specific heat of water, so the energy being transferred to the skin is at a much lower level. You can reject a large portion of this heat by sweating

There used to be a Finnish sauna endurance competition where the temperature was 110℃. It was canceled in 2010 after one contestant died.

https://en.wikipedia.org/wiki/World_Sauna_Championships

This is a big sauna, most of the air is not at that temperature. And I would certainly not attempt endurance in it, but the thermometer on the wall usually is between 235F and 245F

They are not positive for me. Not at all. I feel worse during and after both wet and dry saunas. But then again I have Finnish and Inuit heritage so...

There's nothing magic about saunas. The only thing different is you can choose when you leave.

I agree, saunas are different. People working outside don't have the luxury to do so for only 10-30 minutes a week. And, not all positive: in Finland, a study found that there's around a 1 in 100k death rate per capita where heat exposure was the culprit.

https://pubmed.ncbi.nlm.nih.gov/18471223/

Interesting but you can’t really draw any conclusions on the healthiness of proper sauna use. We also don’t have any data on if people in general are living longer/healthier because of the sauna. Some people die from drinking water too

> Overall, 50% of all cases were under the influence of alcohol. The main conclusion is that death in the sauna is a rare event even in Finland where the frequency of sauna bathing is high.

I was responding to the claim "their effect for health is entirely positive." If you want to shift the goalpost from there, I'm not here for that debate. I love saunas myself, wet or dry.

Also dry saunas go up to 110°C/230°F. On the other side of the spectrum, steam baths/Turkish saunas are set around 45°C (115°F), which feels very comparable to a 90°C (200°F) dry sauna

- Look, this is another gruesome way we could die in the future!

- Ohh, this looks awesome! Tell me more about that.

Tabloids have figured how to scratch the masochistic itch of its readers.

People have been dying from wet-bulb heat events for years. It just hasn't been widely reported because those people tend to be the disabled, sick, and elderly.

I knew it. Please don’t say “we” because it’s not true. But it does make most want to click.

> He acknowledges that the study participants were from central Pennsylvania, so they weren’t accustomed to temperatures and humidity spiking off the charts. Some people living in typically hot and humid climates may be better able to tolerate those conditions. However, he adds, volunteers were also young and healthy, which presumably would have made them relatively more resilient: Age as well as heart conditions, diabetes, and other diseases inevitably bring the threshold down for many. For some of them, 31 Centigrade (88 Farenheit) at 90 percent humidity might be deadly.

This was not a scientifically valid study, as it preselected individuals from a cold climate.

This is nearly as bad as selecting native Inuit from Alaska and conduct a study on handling humid heat ~ pre-biased towards a specific conclusion.

The temperature in my office right now is 28.1 with 86% humidity. I'll start to sweat in a couple of minutes. I rely on air conditioning to keep things more comfortable (at the setting I use, it brings it down to about 24 degrees and 75-80% humidty.)

No, it just means that people from that area cannot handle higher temperatures and humidity. Many parts of the world are not used to higher heat and humidity, and those same places are experiencing both more regularly, so it's quite relevant, and scientifically valid. Pennsylvania is nothing like Alaska. Nor is it the same as Qatar, but that should be obvious to most.

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