Ozone has a very strong odor and can be felt by us at the level of concentration that are not able to harm us. After it is produced in the ozonator and distributed in the room ozone decomposes back into pure oxygen. Ozone, therefore, despite its strength, is not durable - performs its job and disappears.
The maximum, acceptable for people, ozone concentration in the air operating for 8 hours a day and 40 hours per week is 0.2 mg/m3 or 0.1 ppm relative terms. Recommended target level is 0.12 mg/m3 or 0.06 ppm.