What happens during an ozone steam sauna session, and what does it feel like?

A session takes place in a sealed fibreglass sauna that you sit in with the doors closed around your body. Ozone is produced inside the sauna from oxygen supplied by a medical oxygen concentrator: a 500 mg/h generator on a constant 2 l/min oxygen feed brings the whole air volume of the sauna to roughly 47 ppm, and the digital display steps that output in 10 levels of 10% each. The exact figure varies a little with the size and build of the person inside, because they take up part of that air volume.

This arrangement has a name: transdermal delivery, meaning a substance is given across the skin rather than by mouth, injection or breathing. The sauna encloses everything below your neck, so the ozone reaches your skin and not your lungs.

What you actually experience:

• The sauna is preheated before you get in, and the seat height is set to suit you.
• Once the doors close and the neck opening is covered, the humidity rises and you begin to sweat within a few minutes.
• For a first session we suggest 30 °C to 37 °C, depending on your comfort. Only people in good health should go above 37 °C, and ozone begins to break down above about 40 °C, so a hotter sauna is not a better session.
• The figure on the display is the temperature of the air in the sauna, not your core body temperature — the temperature of your deep organs, which the body normally holds close to 37 °C.
• The heat is adjustable throughout. If you are uncomfortably hot, say so straight away, or end the session yourself. To get out, open the doors and step out. To stop the ozone, switch the sauna off at its wall socket once you’re out.

If you feel unwell at any point, follow the steps on feeling unwell.

Our view is that the heat is a bonus for those who enjoy it; the ozone is the reason for the sauna.