There are different types of saunas and steam rooms, with temperatures that can range quite a bit. Typically, safe temperatures range between 78-90°C (180-195°F). Though saunas can get much hotter (reportedly, going up to 160°C 220 °F), that ranges well outside the realm of safety (at least for most people). But let's look into it a bit deeper, because it gets quite complex.
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What is a sauna
A sauna is basically a small room designed as a place where people can enjoy wet or dry experiences, all in very high heat. The sauna, as we know it today, comes from Finland, where many houses have a built-in sauna. But using a sauna isn't as exclusively Finnish as you might think. The practice was surprisingly common during the Middle Age, but dropped out massively due to the fears of spreading syphilis. Because Finland is so cold, the disease didn't really get a strong grip, so the practice remained popular there.
With the Industrial Revolution, the practice changed significantly. Saunas started to incorporate a metal woodstove with a chimney. That's when temperatures really got steaming, reaching 75–100 °C (167–212 °F). As trains became a thing, people also started to move around -- and so did Finns. By that point, sauna was mostly a Finnish and Baltic endeavor, but they took it with them in Europe, and further. Sauna became very popular especially in Scandinavia and the German speaking regions of Europe after the Second World War.
Nowadays, there are several different types of saunas, but the process is largely similar. You have a heater that heats up a stack of rocks which then radiate the heat into the room. Saunas have a vent, usually found near the floor by the heater. This brings in fresh air and limits the humidity build up -- we'll get back to that a bit later. Typically, saunas are dry. Sure, some allow pouring a bit of water on the hot rocks to raise the humidity, but they still classify as dry saunas. Conversely, wet saunas (often called steam rooms) are airtight to keep the humidity close to 100 percent. The air is damp as no humidity can get out, and these saunas have significantly lower temperatures than dry saunas. In recent decades, infrared saunas have also emerged, though many still don't consider them to be saunas.
How come you don't just get burned?!
By this point, some big question marks might pop up. After all, we're talking about temperatures at which water boils, how can the human body tolerate that? Even more, how come people like it?
Well, remember when we said that dry saunas are hotter, but they don't have as much humidity? Think about it this way. You can sit for a few minutes in a room that's 90°C (180°F), but if you put your finger into water that's 90°C, you'll end up with a very nasty burn. Why is that? Water is a much better conductor of heat than air. Both air and wood (which is typically how a sauna is furnished) are very bad temperature conductors, so you can manage it. The rate at which you're accumulating heat is very slow. That's why your body doesn't really mind jumping into a frozen pond after a sauna -- it's just a way of regulating heat.
In a dry sauna, you're basically slow roasting. You're accumulating heat, your body starts to transfer it through the body, and you heat up more and more. Even in water-boiling temperature, you can still manage it for a while -- as long as the temperature of the air, the room and the benches is above the dew point even when water is thrown on the hot stones and vaporized.
In contrast, the temperature for a steam room (wet sauna) is much lower. The North American Sauna Society recommends keeping its temperature to less than 49ºC (120ºF). As we mentioned above, water is a much better heat conductor and we can't afford to heat water at the same temperature as air.
So if you're looking for the hottest saunas, they'll definitely be dry saunas. Some people differentiate between dry saunas and traditional Finnish saunas, but the only difference is that the latter involves pouring a bit of water on the rock, whereas the former does not. They're both, at least in name, dry.
So how hot can it get?
You should always, always be extra careful with the sauna temperature. It can get very dangerous. Don't believe me? You must not have heard of the 2010 World Sauna Championships (yes, people do crazy things like this).
On 7 August 2010, Russian finalist and former third-place finisher Vladimir Ladyzhensky and Finnish five-time champion Timo Kaukonen passed out after six minutes of 110 °C (230 °F) heat, both suffering from terrible burns and trauma. Kaukonen was able to leave by himself, but Ladyzhensky had to be dragged out. He passed out and immediately went into cramps and convulsion. Despite immediate medical treatment and despite resuscitation, he never woke up. Despite being an experienced sauna-goer, and despite having endured similar temperatures in the past, Ladyzhensky was killed by a sauna. The championship was never carried out again.
Are you a bit scared? Good. You should never forget that this practice, while relaxing, and while potentially very healthy, can be very dangerous. Not all saunas are made the same, and two identical temperatures can feel very different depending on the environment and humidity. There is no official maximum temperature for saunas since the practice varies so much, but needless to say -- you should never reach 110 °C. You probably should never even reach 100 °C.
Saunas can be very tiring. Researchers have shown that a sauna session can be just as tiring as working out, which makes it all the more important to avoid extreme temperatures and hydrate.
"A sauna session is a physical strain. Its long-term positive effects are similar to sports activities", explains Ketelhut. Nevertheless, the healthy sweating does not contribute to weight loss: "The effect is too low as there is no muscle activity. Although we lose weight in the sauna, but these are just the fluids that we sweat out. One should rehydrate after a sauna session, though", concludes Dr Sascha Ketelhut, lead author of the new study and a sports scientist at MLU.
However, saunas can be healthy when you're more responsible. A recent study showed that saunas can help improve cardiovascular health, especially in conjunction with exercise.
“The results of this study lend support for the regular use of sauna bathing with regular exercise, and shows promise as a therapeutic adjunct, particularly for those with lower exercise capacities,” says Earric Lee, a Doctoral Researcher in the Faculty of Sport and Health Sciences.
"These results are exciting because they suggest that this activity that people use for relaxation and pleasure may also have beneficial effects on your vascular health," said Setor K. Kunutsor, PhD, of the University of Bristol in the United Kingdom, who also researcherd saunas. "Sauna bathing [at responsible temperatures] is a safe activity for most healthy people and even people with stable heart problems. More research is needed to confirm this finding and to understand the ways that saunas affect stroke risk."
For a dry sauna, 78-90°C (180-195°F) is generally a safe margin for most people. For a wet sauna, it should be less than 49ºC (120ºF).