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Furnace filters by MERV, MPR and FPR, sizes, upgrades and replacement schedules.
Washable filters save waste but most are MERV 8, which catches large dust and pollen and little smoke-size particulate. For allergies or smoke, a disposable MERV 13 is the better buy.
Pollen, dust mite debris and dander are mostly large particles, which MERV 12 and 13 filters catch at 90% or more. Our top allergy pick is the Filtrete MPR 1500 (MERV 12).
EPA suggests MERV 13 or the highest your system can handle. Our top pick is the Filtrete MPR 1900, a MERV 13 1-inch filter; here are five more for different systems and budgets.
A media cabinet holds a 4 or 5-inch filter that reaches MERV 13 with less airflow resistance than a 1-inch filter. Our top pick for adding one is the Honeywell F100 cabinet.
Filter sizes are nominal: a 16x25x1 is about half an inch smaller each way and under an inch thick. Measure the slot, not the old label, and order custom only when no standard size fits snugly.
UV-C lamps aimed at the cooling coil keep mold and bacteria off it; that is what they do well. For cleaning the air you breathe, EPA says a typical home unit's dose is too low. Use them with a filter, not instead of one.
"Electrostatic" covers three different things: disposable pleated filters with charged fibers, washable MERV 8 panels, and powered electronic air cleaners. They perform very differently.
All three sell MERV 13 filters. Filtrete publishes the most performance detail, Nordic Pure sells MERV-rated multipacks, and Honeywell's strength is 4-inch media filters for its cabinets.
A bypass HEPA unit pulls part of the return air through a HEPA filter with its own fan, so it does not choke your furnace. EPA says most MERV 13 filters get close to HEPA results anyway.
Every 60 to 90 days is the usual guidance for 1-inch filters, and Filtrete says at least every 90. Pets, allergies, renovation and smoke shorten it; deep media cabinets lengthen it.
For most forced-air homes, yes: MERV 13 is EPA's suggested minimum and catches at least half of smoke-size particles. The two caveats are your system's airflow and how often the fan runs.
MERV 13 catches the most fine particles and is what EPA suggests; MERV 11 is the safe middle; MERV 8 is for dust and restrictive systems. Here is the table and how to choose.
MERV is a 1 to 16 score for how well a filter catches particles of 0.3 to 10 microns. EPA suggests MERV 13 or the highest your system can handle; here is what each level actually catches.
Compare filters by MERV. MPR (Filtrete) and FPR (Home Depot) are proprietary scales; use the MERV the brand itself prints next to them, because third-party conversion charts disagree.
If you cannot see light through it, it is gray all over, or the system is struggling, change it. EPA says an overloaded filter will not work well and can send air around the filter.
The one widely sold smart filter, Filtrete's Bluetooth model, tracks filter life from airflow and run time. For everyone else, a dated frame and an app reminder do most of the job.
