Whether you’re on the couch, at the office, or on vacation, you can keep an eye on the air quality in your home and adjust your air purifier accordingly for an optimal indoor environment. One of the MinusA2's unique features is the ability to customize the filtration to target your specific concerns. Customized filter is one of the five filters in the MinusA2 air purifier. This bonus layer of protection enhances the cleaning power of your targeted pollutants. Each customized filter has a different proprietary coating or structure which helps target specific allergens or concerns.