You need an oxygen generator/concentrator. It is required equipment.
The oxygen concentrator separates oxygen from nitrogen, supplying it directly into the ozone generating cell. This enables the generator to produce ozone effectively at 6 to 23% concentration by weight. An air compressor pumps ambient air into the oxygen concentrator's input.
If that didn't work: Ensure the compressed air supplied to the oxygen concentrator is free of oil vapors. Install an oxygen filter after the oxygen concentrator and before the ozone generator to protect it from sieve particles if the concentrator fails.
Heads up: Connect the generator using tubing made from material appropriate for ozone and oxygen applications. Incorrect feed gas quality (too much humidity or contamination) will trigger the internal diagnostic system.