The human body emits and receives infrared heat and other surfaces give off infrared in the middle and near infrared range.
Infrared heaters warm the body in the same way as natural sunlight. Traditional saunas raise the temperature of the air to a very high level within the chamber to warm the body. Some people have difficulty breathing in this extremely warm air. Instead of heating the air within the enclosure, infrared saunas heat the body directly. In an infrared sauna, the body perspires and receives all of the healthy benefits but avoids the harmful and extremely hot air of a traditional steam sauna.