WA Lic. INFINHA841B8 400+ Google reviews
Quick answer
- MERV 8: basic dust/pollen. MERV 11: pet dander, finer dust. MERV 13: smoke particles, most allergens — the smoke-season sweet spot if your system supports it.
- Thicker is better: a 4–5" media filter filters more with LESS airflow restriction than a dense 1" filter.
- Change 1" filters every 1–3 months; media filters every 6–12 months; more often during smoke season or with pets.
- A whistling return grille or a filter bowing inward = too restrictive for your blower.
What MERV actually measures
MERV reports the worst-case capture rate across particle sizes. Higher numbers catch smaller particles: pollen and dust mites in the single digits, pet dander and fine dust in the low teens, smoke and bacteria-scale particles at 13+. HEPA is beyond the MERV scale entirely and generally needs dedicated equipment, not a furnace slot.
The pressure-drop trade-off
Filtration is a screen in your system's airway. Denser screens catch more but resist airflow more. Blowers are designed for a certain total resistance; exceed it and you get less heating/cooling capacity, higher bills, frozen coils, and shortened equipment life. This is why 'just buy the highest MERV' is bad advice — the right answer depends on your blower and duct design.
Media cabinets: the usual right answer
A 4–5 inch media filter has several times the surface area of a 1-inch panel, so it achieves high MERV ratings at low pressure drop and lasts six to twelve months. If you want MERV 13 for smoke and allergy seasons, a media cabinet retrofit is usually how to get it safely.
Northwest change rhythm
Our homes run fans nearly year-round (heating season plus cooling season plus smoke events), so filters load faster than the box suggests. Check monthly during heavy-use months. After any multi-day smoke event, inspect the filter regardless of schedule — a smoke-loaded filter chokes the system.
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Family owned · WA Lic. INFINHA841B8 · 400+ Google reviews
Common questions
Can a filter be too good for my system?
Yes — 'too good' meaning too restrictive. If your blower can't overcome the filter's pressure drop, airflow collapses. We measure static pressure to find the highest rating your system genuinely supports.
Are washable electrostatic filters worth it?
They save on replacements, but most rate around MERV 4–8 and lose efficiency if not washed and fully dried on schedule. For allergy or smoke concerns, disposable pleated or media filters perform more predictably.
Where is my filter, anyway?
Usually in a slot at the air handler/furnace, sometimes behind a large return grille in a hallway or ceiling. Some homes have both — only one should hold a filter. We're happy to show you during any service visit.
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Infinity Heating & Air — licensed WA HVAC contractor (Lic. INFINHA841B8), family-owned in Graham. Last updated July 2026.