Tips for buying a sauna

Been browsing for a sauna on my local classifieds. I remember finnish saunas were the best but what about them make them the best... negative ions/lack of positive ions?

Nowadays people are concerned with the EMF from saunas. I found this one but i can't seem to find if it gives off negative ions and grounds out the positive ions.

http://www.radianthealthsaunas.com/

"Radiant Health Saunas™ have been designed to maximize safety and optimize performance based on continuous testing and feedback from our valued practitioners and customers. Radiant Health’s carbon infrared saunas have been independently tested for Volatile Organic Compounds (VOCs) to ensure complete non-toxicity, and have extremely low Electromagnetic Radiation (EMR) or Electromagnetic Field (EMF) levels - lower than Swedish Standards."


Carbon Flow Technology

A common complaint about infrared saunas is the uncomfortable sensation of “cold spots” in the sauna, where no infrared heat waves reach the body and “hot spots” when seated directly in front of the old-style ceramic or metallic infrared heaters. Due to the huge surface area of the Carbon Flow heating panels, literally spanning wall-to-wall, the heat is evenly disbursed and the surface temperature of the heaters is comfortable to the bathers.

The emitter surface area totals over 4300 square inches in our two person model and over 5700 square inches in our three person model. The large surface area allows us to have a lower surface temperature which creates a longer, more beneficial far infrared wave length range. Medical researchers have found that the optimal micron output range is between 7 and 14 microns, often called the Vital Zone.