9pk Replacement Furnace Air Cleaner Filters for high efficiency air cleaners by Aprilaire and Space-Gard. These filters can cost up to $40 per filter if you purchase through your heating contractor.
Equivalent Air Filter:
Aprilaire: 401
Fits Models-
Aprilaire and SpaceGard Air Cleaners: 2400
Lennox: PMAC-12C (X0577)
#SG4
WHAT DOES MERV MEAN?
ASHRAE which is the American Society of Heating,
Refrigerating and Air-Conditioning
Minimum
Efficiency
Reporting
Value
MERV 1-4 (Greater than 10 microns): pollen, dust mites, sanding dust, carpet fibers
MERV 5-8 (3-10 microns): mold spores, hair spray, cement dust, powdered milk
MERV 9-12 (1-3 microns): Legionella, lead dust, coal dust, auto emissions, welding fumes
MERV 13-16 (0.3-1 microns): bacteria, tobacco smoke, insecticide dust, copier toner
One micron equals one thousandth of a millimeter. To put it into perspective what particle sizes these filters will remove from the air, you need to consider that the thickness of human hair is between 50 and 100 microns! As shown above, a MERV 11 rated filter will remove particles that are down in the 1 micron size range! (That's 1/50th or 1/100th of the thickness of a hair!)