One of the best kept secret of a ductless mini split system is their hidden air filtering and allergen removal capabilities. Most standard mini-split units have a hybrid catechin pre-filter and active carbon filter, using antioxidants to absorb odor-causing gases. The filter inside the mini-split systems removes many of the airborne pollution and allergens, leaving you with clean fresh air.
If you have an allergy problem or are sensitive to pollen in the air, then the ductless mini split system can make your life and health better. The only maintenance that you have to do is open up the mini split unit, take out the filter, and clean it every 3 to 6 months.
Reference
http://www.fujitsugeneral.com/wallmountediaq24-30.htm