What Level of Ozone is Safe?

Ozone is regarded as safe and has been awarded a GRAS rating (generally recognized as safe) by the Food and Drug Administration. The Occupational Health and Safety Administration requires that workers not be exposed to an average concentration of more than 0.10 parts per million (ppm) for eight hours. 

Because the concentration of ozone required for deodorization and for fungus and mildew inhibition is 0.3 to 1.5 ppm, it is recommended that hotel personnel not be in the area when ozone equipment is being used. Ozone generators come with timers. According to Tampa, Fla.-based Zontec Ozone Inc., also a seller of ozone products, most odors can be eliminated in less than 15 minutes. It is generally safe to return to the treated area about an hour or two after the machine has shut off-once the ozone has reverted back to oxygen. 

Because ozone, in high concentrations, can be an irritant to some people, it is recommended that as little as possible be used to treat an area. Due to the oxidizing nature of ozone, there is no benefit to over saturating an enclosed area for anything less than garbage odors or fire or flood restoration products. Because ozone is made up entirely of oxygen, it can only revert back to natural oxygen once the ozonation process is completed. If odors persist after treatment, an ozone generator can be used over and over until the odor is gone. Ozone shock treatments-ones using high ozone levels that require an unoccupied space-are needed to remove stubborn odors.

Ozone has a bleach-like odor when its concentration level is unhealthy. Do not, however, use smell as a test. One person's ability to smell is different than the next person. One need not smell the ozone from a generator for it to be effective. According to the Environmental Protection Agency, ozone can cause chest pain, coughing, shortness of breath and throat irritation at unsafe levels. Some ozone generators generate nitrogen oxide. Be sure to ask your vendor about the levels produced. Certain levels of nitrogen oxide can aggravate respiratory conditions. Airing out a room after an ozone treatment can ensure a safe environment.