Human discovery has invented many preventive and safety equipment. With this ideology, the air purifier was invented to protect us from breathing contaminants and impurities in the air or at least minimize it. From the use of a filter media to trap visible particles, air purifiers have evolved into the usage of HEPA filters to trap very fine particulates which are not visible to the naked human eyes and activated carbon filters to absorb VOC that causes bad smell. These are the 2 main filter media components in any air purifier today.
There are 2 more main components in an air purifier that makes it do what it does best to filter impurities from the air; the design of the device which promotes airflow through its filter and the fan motor it is equipped with. This sounds very simple but without the proper assembly of all these 4 main components, it would just be another redundant electrical device
With these being said, there are also many different ratings in the components used. HEPA filters have ratings where its efficiency and efficacy to filter and trap particulates down to sub-atomic size are tested. The activated carbon filters used are evolving too from charcoal pieces to pleated form activated carbon. Together with its design and fan motor used to complete an air purifier, the end product can be tested in an independent lab to obtain certifications of compliance.