The dry sauna keeps the humidity about 20% and is very dry. Just don't keep it too dry or you might experience respiratory difficulties. The dry heat is more easily tolerated by our bodies, as high humidity in the air transfers heat more efficiently than drier air and, therefore, your system can get too hot. Think health bennies here with your increased heart rate and metabolism. And if you are trying to lose weight, forgo the thirty minute walk in the dead of winter, and instead grab a magazine and plop down in your sauna for the same caloric advantage. Your muscles will receive a vacation as well, relaxing enough to rejuvenate you for your next athletic endeavor. The Swedes are sold on the perks of a dry sauna...when their national athletes are competing away from home, they take a dry sauna along to keep down injuries along with an ability to tolerate a more intense athletic schedule.
The more typical dry sauna is the Finnish sauna. You have an enclosed space with a heater on the floor that heats special rocks. When it becomes too dry, you just pour some water over the rocks for instant steam and humidity. The Finnish sauna is larger than the infrared version, usually made for four or more people and are usually built outside your home space.
The dry sauna can also be an infraredsauna. Also known as FIR, it heats your body without heating the air around you similar to the way the sun utilizes the wavelengths of light for heat. It is a more efficient use of energy (healthy for your power bill) and very "hot" in the new home market. The infrared sauna's heat source warms ceramic tiles in the wall of the sauna that make for an even heat without the need for a fan. They use less power, lower temps, heat faster with less maintenance than the standard dry sauna that depends on a floor heater and rocks for heat generation.
Infrared saunas can warm your deepest tissues and help heal. An infrared sauna is healthy for the whole family, including anyone with respiratory problems. Another perk of the infrared sauna is its control...you can set the time and temperature of the unit for what is best for you. Any time there is a spike in temperature the unit will shut down as well. Add in the other benefits of the dry sauna, including the expansion of blood vessels and raising your internal temperature high enough (110 degrees F) to burn fat, you may want to investigate the infrared sauna.