HVAC air filter unit uses disposable filter medias mounted on frames, panels, as pockets or cartridges. In the case of the panels, the frame of the panels can be re-usable while the filter media itself is disposable.
The filter media can be dry or oil coated. In the case of the oil coated media, the filter media is wetted with oil or coated with adhesive gel to improve their retention properties.
They can be used in a primary and secondary prior to an HEPA filter module of an air filter unit depending the application and the dangerousness of the filtered particles.