The medium efficiency mechanical filters and HEPA filters can last as long as six months to a year before they need changing. Electrostatic precipitators have the disadvantage of producing some ozone, a known pollutant. Most of the oxygen molecules in the air are paired, and this is what we need to breathe. When three oxygen molecules are combined, the compound is called ozone. It is not good to breathe.
Ozone is released mainly when the units make their characteristic popping sound.
This occurs when electrical arcing occurs inside the unit. Wherever there is a spark, there can be ozone produced, so ozone can also be given off by electric motors. Since this is difficult to eliminate entirely, some manufacturers can supply a small activated carbon filter that can be added to their electrostatic precipitator to handle the ozone. The carbon reacts with the ozone to change it back into breathable oxygen. The last type of particulate filter uses static electricity to capture dust.