Sizing & CADR · reference
Whole-House or Room Air Purifier?
A single unit in the hallway cannot cover a home, and the reason is structural rather than stubbornness: EPA publishes a minimum per room, not per house. There is no published CADR for "the flat", because a flat is not the unit of measurement.
Whole-house filtration exists, but it is a different job done by different equipment. Here is the honest divide.
One minimum per room#
The published table matches 65 cfm to 100 square feet, 130 to 200, 195 to 300, and so on to 390 at 600. Each row is a room. A hallway unit with a large CADR does not discharge that duty on behalf of the bedrooms; it serves the space it stands in, and doors do the rest.
If you want the bedroom cleaned to the minimum, the minimum has to be delivered in the bedroom. That is a portable unit's job, sized to the room's row.
What whole-house systems actually are#
Whole-house filtration means the HVAC system: filters in the return duct, cleaning air as it circulates while the system fan runs. The relevant rating is MERV, which rates how well the filter captures particles. Filters rated MERV 13 and above must demonstrate at least 50% removal efficiency for the smallest particles tested.
Notice what is missing: any figure connecting a MERV number to a room size. EPA publishes no MERV-by-room-area table, because the question does not work that way. find MERV 13 furnace filters on Amazon if your system takes them, that is the whole-house route, honestly labelled.
Suggested next step
Compare what the table asks for
Search listings for the published minimum your room needs, then check the smoke CADR on the shortlist before anything else.
The honest comparison#
HVAC filtration treats the whole home's air, but only while the system fan runs, and its capture is rated by MERV rather than delivered per room in cfm. A portable unit delivers a published CADR into one room, continuously, at whatever speed you choose. Neither figure converts into the other, and no published equivalence exists.
The jobs differ, too. Duct filtration runs whether or not you are in a given room. A portable unit runs where you are, which is where the bedroom minimum actually has to be met.
Which one fits your home#
- Ducted home, system fan in regular use: a MERV 13 or higher furnace filter is the whole-house background. It is filtration, not sizing, no row of the table applies to it.
- Specific rooms where you breathe and sleep: portable units, each sized to that room's published row, rounded up between rows.
- Rented flat, no ducts, no system fan: portables are the only route. There is no whole-house answer without ducts.
- Mixed case, which is most homes: both. The furnace filter does the background; the bedroom unit meets the bedroom's published minimum.
Questions people actually ask
Sources
- U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition), retrieved 2026-08-30
Quoted and transcribed, never paraphrased into new numbers. This site does not interpolate between published figures.
Suggested next step
One more angle before you decide
The minimum is settled, spend the rest of the decision on noise, filter cost and the smoke CADR.
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Printed from https://roomandfilter.com/sizing/whole-house-vs-room-purifier, “Whole-House or Room Air Purifier?”. Figures from U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition), retrieved 2026-08-30. No prices are shown on this site, by policy.