Is ozone dangerous?

Ozone at high levels in air is harmful, and the thing that matters is not breathing it in. Ozone is toxic to the lungs if inhaled; medical applications must use strictly controlled administration methods (injections, topical, transdermal or autohemotherapy).

The risk profile of a session is mostly about containment and screening rather than the gas itself:

• Airway exposure. Managed by keeping the head outside the cabinet, covering the neck opening, and ventilating the room.
• Off-gassing. Some ozone escapes the cabinet into the room, past the neck opening and door seals and when the doors open at the end. That matters more to an operator in the room all day than to a client having one session.
• Gas purity. Ozone should be produced from a medical oxygen source; with ambient air, impurities pass through the generator too.
• The person in the sauna. Several conditions are contraindicated, mostly because ozone thins the blood and because sauna heat raises the heart rate.
• The equipment. Insist on equipment standards and trained operators.

Two design points limit how much ozone is left at the end: the generator stops producing new ozone five minutes before the session ends, and ozone’s half-life in a hot steam sauna is roughly 10 to 20 minutes, so much of it has reverted to oxygen by the time the session finishes.

Ventilation handles the rest. Industrial ozone plant instead uses an ozone destructor, a unit that passes exhaust gas over a catalyst to turn residual ozone back into oxygen before it is vented. We do not think one is cost-justified for a sauna, and on nearly twenty years of operating these saunas we consider normal room ventilation sufficient — an open door and window clear what escapes. We recommend a minimum room of 2 m by 2 m, with 3 m by 3 m or larger as the optimum.

Like any heat or wellness session, ozone therapy carries risks. That is what the screening list and the operator training are for.