Ozone is natures cleaner. Its oxygen in a triatomic form that loses an O1 to anything it comes in contact with which is oxydizing and killing pollutants and leaves biproduct of O2 which is what we breathe and need. CA has higher levels of ozone because they have more smog and ozone is naturally trying to cleanup smog w O3. Being afraid of a little bit of O3 seems unnecessary. Ionizers produce very little ozone anyway unless they do it by ultraviolet or corona discharge making it an Ozone generator which this is not.
For maximum performance, we suggest that you keep it on continuously. You may remove it from the plug once a month so that you can clean out the dirt that it may create on the wall.
The useful life expectancy of the product is 2.5 to 3 years.
Unfortunately, the product does not eliminate molds and mildew.