Choose an air purifier with a true HEPA filter and a CADR rating that matches your room: a common rule of thumb is a smoke CADR of at least two-thirds of the room's area in square feet (for example, 100 or more for a 150 sq ft room). Check noise levels at the setting you'll use, the yearly cost of replacement filters, and an activated carbon filter if you want to reduce odors.
Air purifiers can reduce dust, pollen, pet dander and smoke particles. The key is sizing it correctly.
HEPA filters
True HEPA filters capture at least 99.97% of particles at 0.3 microns, the hardest size to catch. Be wary of vague labels such as “HEPA-type” or “HEPA-like.”
CADR and room size
CADR (Clean Air Delivery Rate) is tested for smoke, dust and pollen. A widely used rule:
Smoke CADR ≥ 2/3 × room area (sq ft)
| Room size | Minimum smoke CADR |
|---|---|
| 150 sq ft | 100 |
| 250 sq ft | 167 |
| 350 sq ft | 233 |
| 500 sq ft | 333 |
For allergies, asthma or wildfire smoke, size up.
Odors and gases
Choose a purifier with an activated carbon filter. More carbon by weight works better.
Noise
Check decibel (dB) levels on the setting you’ll actually use. A purifier running on low in a large room cleans less air.
Running costs
- Replacement filter price and lifespan
- Energy use: look for efficient models
Features
- Air quality sensor and auto mode
- Sleep mode with dimmed lights
- Filter replacement indicator
Avoid
Ozone-generating “air purifiers” can irritate the lungs; avoid devices that intentionally produce ozone.
Common questions
What does CADR mean?
Clean Air Delivery Rate: how much filtered air a purifier delivers, measured for smoke, dust and pollen. Higher CADR cleans a room faster.
What size air purifier do I need?
As a rule of thumb, choose a smoke CADR of at least two-thirds of the room's area in square feet. Bigger is better for allergies or smoke.
Do air purifiers remove odors?
HEPA filters capture particles. Odors and gases need an activated carbon filter, and heavy carbon layers work best.