A HEPA air purifier uses a fan for pulling the ambient air in and passing it through a series of air filters. Unlike a HEPA filter that uses physical mechanisms, An air ionizer, on the other hand, uses electrically charged ions that bond with impurities floating in the ambient air.

Since a HEPA air purifier uses a physical filter, the maximum area it can cover is not as wide as an Ionizer.

HEPA Air Purifiers require more maintenance, which increases the yearly maintenance cost.

The major critic of the Air Ionizers point out to the lack of a collection plate in some of the cheaper models. However, the top-end Air Ionizers come with a collection plate which ensures the balance tilts in the favour of Ionizers in the argument of the best Air Purifiers.