Safe use of an ozone generator requires good ventilation to prevent ozone from reaching dangerous levels. Most household ozone generators do not create significant amounts of ozone gas, but even the trace amounts created by these devices can trigger respiratory effects in susceptible people.
Ozone is an unstable molecule consisting of three ozone atoms. It disinfects because it is highly reactive, and when it comes in contact with another element, one oxygen atom tends to break away and bond to whatever it touches. This can oxidize bacteria and other microorganisms, leaving pure oxygen remaining. However, it can also irritate lungs and mucous membranes, causing shortness of breath in those who suffer from asthma and other respiratory disorders. In addition, some compounds react strongly to ozone, oxidizing into potentially hazardous substances that can pose a greater risk to human health.
Ozone generators make poor air purifiers, because they cannot do anything about dust, pollen, mold spores and other physical air contaminants. The relatively low levels of ozone produced by household ozone generators are also somewhat ineffective at disinfection. Commercial ozone generators produce high levels of the gas, but also require operators to wear protective gear and stay out of treated areas during disinfection.