Ozone and oxygen
Ozone generator / corona discharge
An ozone generator converts oxygen into ozone at the point of use. The usual method is corona discharge: an alternating high voltage is applied across a gap containing a dielectric barrier, creating a cold plasma that splits O2 molecules, whose fragments then form O3.
Also called ozonator, corona discharge generator, dielectric barrier discharge, CD generator
How corona discharge works
A high alternating voltage — the Dégremont water treatment handbook gives 3 to 20 kV — is applied between two electrodes with the feed gas flowing between them. One electrode is coated in a dielectric such as glass or ceramic, which prevents an arc forming and instead spreads a cold plasma across the whole surface. Energetic electrons in that plasma dissociate O2 molecules; the free oxygen atoms attach to intact O2 molecules to form O3. The process is often called dielectric barrier discharge.
Feed gas decides the output
The same handbook gives typical yields of roughly 3% ozone by mass from an air feed and roughly 10% from an oxygen feed. An air feed also produces nitrogen oxides — up to 500 ppm by volume, mainly N2O5 and N2O — and with moisture present, nitric acid that deposits on the dielectric and eventually makes it conductive. That is the engineering reason for the oxygen feed: it keeps the output clean and the generator healthy.
In our saunas
The generator is built into the cabinet rather than sitting beside it as a separate box, and is fed by the external oxygen concentrator at a constant 2 litres per minute. Output is set across ten levels on the display, each level stepping the generator by 10% of its 500 mg/h maximum. To check that it is still producing, hold a latex glove in front of the ozone outlet for a few seconds: a hole should appear as the ozone oxidises it. Use that rather than smell — people working around ozone become desensitised to the odour.
Why it matters here
This is the part of the cabinet that actually makes the ozone, and it sits out of sight. Knowing roughly how it works is what makes the glove test and the airflow alarm make sense when you meet them.