The numbers
What a MERV 13 filter is actually rated to do
Filters are graded by ASHRAE Standard 52.2, which measures how much of each particle size range they remove. These are the published minimums for MERV 13 — not our claims, the standard's.
The bottom bar is the one that matters for smoke, because fine particulate lives in that range. Filters below MERV 13 are not rated in it at all.
Read the air-quality page
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3.0 – 10 µm≥ 90% removed
Dust, pollen, larger debris.
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1.0 – 3.0 µm≥ 85% removed
Mould spores, fine dust, some bacteria.
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0.3 – 1.0 µm≥ 50% removed
Smoke particulate. Nothing below MERV 13 is rated here.
Source: ASHRAE Standard 52.2 minimum composite efficiencies for MERV 13.