Ozone gas is derived from the air we breathe or pure oxygen. Due to its unstable structure, it reverts back to its raw material, oxygen, after completing its task. It is a natural disinfectant that leaves no residue and, unless continuously inhaled, is not harmful to human health.

The EPA, OSHA, USDA, and ACGIH in the United States have determined that exposure to ozone levels of 0.10 ppm for 8 hours has no adverse effects.

In a 9 m² room where one person is sitting, the ozone concentration can be raised to a maximum of 0.096 ppm. This level is below the threshold harmful to human health. As the room size increases, the number of people rises, and the temperature increases, this ratio decreases further.

The ozone concentration in the environment should be adjusted based on the size of the space and the concentration of undesirable substances. To ensure proper hygiene, it is recommended to maintain a high ozone concentration (0.2 – 0.3 ppm) when the room is unoccupied and to stop the generator 30 minutes before the space is used. At other times, an ozone level of 0.05 ppm will prevent the formation of new bacteria and germs.

In a 1998 article published at Pennsylvania State University, they examined the claim that ozone, proven to kill microbes in water, should also be effective in the air at similar concentrations. The results are summarized below.

The E.coli (top) and Staphylococcus aureus (bottom) cultures exposed to ozone in the air. The numbers represent the exposure time in seconds.

The death curves for E.coli and S. Aureus obtained in experiments showed that the minimum effective ozone concentration in the air for bacterial sterilization is around 0.1 ppm, which is close to the effectiveness of bacterial sterilization in water.

Observations conducted in schools with and without ozone-circulated air in St. Louis, USA, yielded the following results: