The short answer
Use the best furnace filter your system handles (MERV 11 to 13, ideally in a 4- or 5-inch cabinet) for the whole house, and a HEPA purifier in the bedroom for the room where you spend the most hours.
Side by side
| Furnace filter / media cabinet | Room HEPA purifier | |
|---|---|---|
| Covers | Every room on the system | One room |
| Works when | The blower runs | Always, if left on |
| Fine particles | Good at MERV 13 | Very good (HEPA) |
| Running cost | Filters only | Filters and electricity |
Making whole-house filtration work harder
- Run the system fan on 'on' or a circulate setting during allergy or smoke events.
- Upgrade to a 4- or 5-inch media cabinet for MERV 13 without the resistance.
- Seal leaky return ducts so air doesn't bypass the filter.
Products mentioned
Questions readers ask
Is a whole-house filter enough for allergies?
It helps, especially at MERV 11 to 13; a bedroom HEPA purifier adds the most relief where you sleep.
Can I put a HEPA filter in my furnace?
True HEPA is too restrictive for most residential systems; MERV 13 in a deep cabinet is the practical whole-house option.