18x18x1 Furnace Air Filters MERV 12 Pleated Plus Carbon 12 PackNordic Pure 18x18x1 MERV 12 Plus Carbon air filters are made of a dual material where the MERV rated material has been fused together with a carbon layer. This results in less flow restriction and 33% more surface area for cleaner smelling air. It will help eliminate unwanted odors as well as trap most airborne dust and particulate matter for fresh, clean air. Odorous gases and vapors (VOC) are attracted to and held by the activated carbon material