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?

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.

“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.

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.

“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,”