September 25, 2022

What’s the difference between a regular sauna and an infrared sauna?

I’ve heard a lot of wild ideas about the differences between a regular sauna and an infrared sauna. Most people have no idea what they’re talking about. They rage wildly about infrared saunas exposing your body to, get this, electromagnetic radiation. Eeeek! Let’s take a look at both and realize what actually happening using less emotion and a little more science. OK?

How traditional saunas work

Traditional saunas (mostly referring to Finnish dry saunas) are constructed of an enclosed room (usually made of wood) and a heat source. The heat source was a fire with rocks thrown on top. The rocks retain the heat and help maintain a constant temperature. Today they look more like the one in figure 1.

Harvia KIP60 6kW Electric Sauna Heater

 

Figure 1 – Electric heater used in modern saunas

The heater in figure 1 is powered by electricity with a heating coil much like the one in your electric oven. It is a piece of metal that heats up due to resistance to the electricity passed through it. They often glow a red-orange at higher temperatures (>190º F.) When they’re in a sauna they are covered up, but if you look closely, you’ll see the dull red-orange glow through the rocks.

The sauna works by air passing over the glowing element. Convection carries the air upwards out the top of the heater, while cooler air is brought in from below. You’re never really exposed to any radiation coming from the heating element. The red-orange glow is photons being emitted from the element as it heats up. If you could see in light in the 700 nm – 900 nm, the element would probably be even brighter than visible light. That light is Infrared radiation.

It’s not the heat, it’s the humidity.

So, the air is heated up and your skin is exposed to the very warm air. Throw a little water on the rocks and it quickly flashes to steam. This steam makes the air very, very hot. It’s the humidity, that makes the air seem so much hotter. That’s because your body depends on evaporation to keep cool. Humidity interferes with this cooling effect. In fact, at 100% humidity, you can’t cool yourself down through evaporation.

It’s all a lot of hot air.

A dry sauna is based around being exposed to hot air. Sometimes nearly 200º F.  

How Infrared Saunas work

Infrared saunas use a slightly different approach to heating your body.  Whereas traditional saunas depend on convection to heat your body, infrared saunas transfer heat via radiation. Ooooh! Radiation.  Not as scary as it sounds.  (Notice that the air in the lower portion of the traditional sauna is noticeably cooler than the upper portion.)  Have you ever stood in sunlight and gotten warmed up?  That’s radiation, including the infrared wavelengths used in an infrared sauna.  The same thing happens when you stand next to a fire to get warm.  You don’t put your hand into the flame, but you still feel the heat, don’t you?  That’s radiant heat transfer.  It’s actually, like the heating element in the traditional sauna, except you’re being heated instead of the rocks.  This is why you don’t need such high temperatures in an infrared sauna because the heating element is heating you directly.  Actually, you can simulate the effects of infrared saunas by laying in direct sunlight with/without clothes on.  But, since infrared saunas don’t emit ultraviolet light that causes sunburn, you not likely to get a sunburn from the sauna.

Conclusion

There are differences between the two types of saunas in the mechanism used to heat your body.  It’s nothing new, nothing you haven’t been exposed to your whole life.    Both types of saunas are beneficial.  There is no real danger from either type of sauna.  There’s always concern when you have red hot electrical elements in close proximity to you.  Especially if you throw water onto the hot rocks and it flashes to steam.