Sometimes it is difficult to figure out whether true hepa filters are being used. There is a new tendency by manufacturers to misuse the term HEPA for filter technologies that are not performing to the standards of the Institute for Environmental Standards, e.g. xxxxHEPA,or HEPAxxxx. The disadvantage is that this filter technology gets less efficient with use, as the fibers loose their electrostatic charge as they are getting soiled. This filtration technology uses ionization to charge dust particles and then metal plates or filter media, which carry an opposite charge to collect them. When the collection surface gets dirty this efficiency drops significantly.
Electrostatic precipitators can generate ozone.
D. Ionizer Ionization by itself uses high voltage to negatively charge airborne particles. Since pure ionizers capture no particles, charged particles are simply released into the room where they tend to attach to surfaces. This means that ionizers may only have a temporary effect of eliminating particles from the air. The EPA also draws attention to the fact that these charged particles when inhaled may have a higher propensity to get trapped in our lungs and become harmful to our lungs. Just because an air cleaner has a hepa filter, does not mean they are all created equal.