Who, What, Why: How hot can a sauna safely get?

Woman in sauna It is not unusual for sauna users in Finland to enjoy temperatures of 100C

A competitor at the World Sauna Championships in Finland died after collapsing with severe burns in 110C heat. But how hot can a sauna safely get?

Sitting in a room with temperatures hot enough to make water boil may sound crazy but that is exactly what participants at Finland's World Sauna Championships have been doing for more than a decade.

Five-time champion Timo Kaukonen had become adept at enduring the tournament's 110C (230F) heat, lasting over 16 minutes in 2003.

However, this year, the Finn collapsed along with Russian rival Vladimir Ladyzhensky six minutes into the final round. Mr Ladyzhensky later died in hospital.

Organisers insisted afterwards that it was not unusual to have such high temperatures in Finnish saunas.

Most sauna users stick to temperatures of around 80C for periods of five to six minutes, according to Finnish Sauna Society chief executive Kristian Miettinen.

However, a self-confessed "sauna freak", he usually heats the room to 100C, while others regularly prefer short three to four-minute bursts at 130 to 140C.

The Answer

  • Some hardened sauna users can stand temperatures up to 160C - for short spells only
  • Prolonged exposure to extremely high temperatures may cause core body temperature to become too hot, leading to collapse and even coma
  • If too humid, can also cause burns

"Heavy bathers in favour of the hottest temperatures always wear felt caps and slippers because the wooden surfaces tend to get very hot.

"How long you spend in there depends on your physical construction. Then you must shower, or jump into a lake or the sea."

The society recommends that people with health complaints such as heart disease, high blood pressure, asthma or skin disease stick to "moderate" temperatures of below 90C, while pregnant women should keep the heat below 70C.

However, Mr Miettinen says he cannot understand how a temperature of "only 110C" could lead to someone's death, when people have safely enjoyed heat at 160C.

Informal competitions often take place among young Finns but those involved know when to stop and cool down, he says.

However, his organisation has spoken out against the World Championships, which he complains has "nothing to do with sauna bathing".

German competitor Silvia Pfuhl The Finnish Sauna Society criticised the world championships

"It's an extreme competition - a test of heat stress endurance," he says, adding that the entrants had repeatedly exposed themselves to high temperatures throughout the day.

If their body temperature rose to dangerous levels, this could have proven fatal, according to John Brewer, professor of sport at the University of Bedfordshire.

While the core body temperature is between 37 and 38C, a rise of just four degrees could cause hyperthermia (overheating), collapse and coma, he says.

"The main defence mechanism is sweating - the loss of that latent heat into the environment from evaporation of sweat that causes the body to stay cool," says Prof Brewer.

During exercise, for example, sweating helps to regulate the body temperature below dangerous levels at about 39C.

Problems arise when something interrupts this process - for example, dehydration.

'Dumbest sport'

Heat and humidity can also affect the efficiency of sweating because the difference in temperature between the body and outside environment is reduced, making it harder for the sweat to evaporate.

In this case, the body sends hot blood to the surface of the skin in a bid to cool it.

'My back seemed to have ignited'

American sportswriter Rick Reilly entered the competition three years ago, concluding that it was "possibly the world's dumbest sport".

In his book, Sports from Hell, he describes how he watched a fellow American emerge from the sauna with burns to the skin under his nose, his ears and back, before his own turn came around:

"I tried to stare at the rocks and not blink, because blinking hurt. I tried to take very few breaths, because breathing hurt. I was sure flames were coming out of my mouth. My back seemed to have ignited."

"Blood vessels in the surface of the skin dilate and that's why people go red," says Prof Brewer.

However, this means the heart is pumping more quickly to supply blood to both the skin and muscles. And if this continues too long because the body keeps getting hotter, the brain can be starved of blood and oxygen - causing collapse.

Prof Brewer believes this could have happened to the sauna contestants.

"You're not going to sweat properly in that environment and the extreme heat could have caused the body temperature to rise to that level," he adds.

"It's a salutary lesson for people not to do extreme activities like this."

Dr Keith Judkins, injury prevention officer at the British Burn Association, says he is not surprised competitors suffer burns.


Question mark

A regular part of the BBC News Magazine, Who, What, Why? aims to answer some of the questions behind the headlines

"You get serious tissue damage within 10 seconds from contact with water at 60C (140F), so it must be the very dry heat that makes it tolerable," says Dr Judkins, of the burns unit at Pinderfields Hospital in Wakefield.

During the competition, water was poured on the stones in the stove every 30 seconds to intensify the heat, which would also have increased humidity.

Comparing 110C to a "cool oven", Dr Judkins says this "cooking temperature" would cause burns with heightened humidity.

But he adds that even if they did not suffer burns quickly, the competitors would have taken their bodies to the threshold of their tolerance levels and put themselves in danger of hyperthermia.

Below is a selection of your comments

The world championships are pretty extreme but sitting in a 100C+ sauna is not unheard of. I like to keep mine between 85 & 90C with a high velocity of air venting around so that the loyly ("steam" is the only way to translate it) dissipates quickly. Then go in for around five to 10 minutes, depending on the outside temperature (and the company) for about three or four visits. As for rolling in the snow? Tried it once but wasn't for me, I prefer swimming in the sea or lakes.

Smirker, Rauma, Finland

It seems to me that competitions like this have ignored the idea of sauna altogether; that is, the sauna is a brief practice aimed at relaxation, a time to be quiet or enjoy mellow conversation with friends. Unfortunate incidents like this are likely to put some people off this delightful ritual forever, which is really too bad.

Meredith, Seattle, Washington USA

I have gone into saunas that were 150C. When I was younger. We always try to stay longer than others but you have to go if you can not take it. There were days we did it for a long time but not every day. Keep the competition but have a doctor to check competitors.

Pekka Sjoman, Canada, born Finland

It's not really a sport but more of an tradition such as the one in England where competitors chase a block of cheese down a steep hill. These are traditions, this is why competitors sign forms with terms and conditions. They want to be part of it.

Kalle Karppa, Glasgow

Some sports border total madness. This is one of them. Exposure to 100C of dry heat, even to a seasoned person, for more than five minutes is "always" a significantly dangerous adventure. Death is then a highly possible happening and should not be described as unfortunate.

Dr Muruka Kays, Nairobi, Kenya

It is the combination of humidity and temperatures in saunas that is important, not just temperature. Turkish baths have modest temperatures such as 50C and 100% humidity and Finnish saunas in excess of 100C (106C is the hottest I've sat in) but extremely low humidity. I can assure Prof Brewer that over 100C in humidity less than 5%, I sweat furiously. Just as I sweat copiously in Hong Kong at 29C and 99% humidity. But have a sauna in excess of 100C and have too high a humidity and danger lurks. In Germany where I have frequently used saunas, only staff are allowed to add water and therefore raise the humidity, in the saunas operating above 90C.

Andrew E, Surrey, UK

Many of us who have used saunas at 110C will find i difficult to make sense of his news story. Dry saunas are tolerable because the very dry air has a lower thermal conductivity than moist air and the copious amounts of sweat produced by the body evaporate quickly and the latent heat of evaporation cools he skin. Pouring water over the heater increases humidity in the sauna, increasing heat transfer to the body and slowing the rate of evaporation. It's basically as simple as that.

Geoff Lake, Carbost, Scotland

I am that guy from Rick Reilly's book. The competition was extreme and it's not for everyone. I do not regret having done it. I trained for a year in my own sauna at 110 degrees, as I have read the rules on their website. However, I don't understand one thing; how can they have BOTH collapsed at the same time after only six minutes? Timo (the five-time champion) had endured 12+ minutes in this temperature in the past competitions. He had even done it on live TV in Germany on stage. 110 degrees cannot kill or even make a trained man sick after only six minutes. There must have been something else.

Rick Ellis, New York, United States

Actually, it was not the heat that killed the competitor but the water thrown on the stones above the stove every 30 seconds, creating boiling hot steam, which can actually burn your skin. Throwing water onto the stones (which are actually quite a bit hotter than the room itself) with a scoop is a normal procedure, but only once or twice during your stay in the hot room. In the final they did it every 30 seconds, 12 times in all, which must have made the air thick with steam, with no time for it to 'cool down'.

Kimmo Kosunen, Plymouth, UK

I had never been in a sauna before, so when I found an unoccupied one in our hotel in Norway, I thought I'd give it a quick try. The thermometer said 105C. It would be extremely painful to put any part of your body into a liquid at that temperature, so I was very surprised indeed at how bearable, and even comfortable, it was to be in a room where the air is that hot. Although I didn't stay in for long, I understand now how these seemingly insane temperatures are quite tolerable, at least for short bursts.

Paul G Robert, Cambridge, UK

More on This Story

In today's Magazine

The BBC is not responsible for the content of external Internet sites


BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.