Which air purifier is right for a bedroom?

Size the unit by CADR

CADR stands for clean air delivery rate. The EPA says it measures how quickly a unit delivers filtered air, is usually rated at the highest fan speed, and that a higher number serves a larger area. The agency’s chart, based on an 8-foot ceiling, gives these minimums:

For higher ceilings, choose a higher CADR. If you plan to run the unit on the lowest speed at night, a larger unit gives you headroom. Our air purifier room size calculator does the arithmetic for your room.

Check noise at the speed you will use

You will run a bedroom unit while you sleep, so the low and “sleep” settings matter more than the maximum. The EPA notes that noise ratings depend on fan speed, and that around 50 decibels is roughly the sound of a modern refrigerator. A listing that only gives noise at the lowest setting tells you less than one that lists each speed. Look for a sleep or night mode that lowers the fan, and compare it to how quiet your room is.

Lights and display

Many units have bright indicator rings or a screen. Look for a display that can be dimmed or turned off, or a night mode that does it automatically. Check the control scheme too: some units reset to full brightness after a power loss.

Filters, ozone and certification

• Particle filter. Look for a pleated high-efficiency filter that the maker names, and a CADR claim that an independent program verifies. The AHAM Verifide program lists room air cleaners that an independent laboratory has verified against the maker’s claims for the suggested room size.
• No intentional ozone. The EPA advises avoiding air cleaners that intentionally produce ozone, which it describes as a lung irritant. Ionizers, electrostatic precipitators, UV lights and plasma units can emit some. The California Air Resources Board and AHAM publish lists of devices that emit little or none.
• Carbon layers. A carbon layer can help with some odors, but the EPA notes that no widely used rating exists for gas removal, so treat the claim as a feature, not a measured result.
• ENERGY STAR. It means a unit meets EPA energy efficiency guidelines, and does not indicate how well it cleans air. The EPA says it does not endorse manufacturer claims of healthier indoor air.

What it costs to run and maintain

ENERGY STAR says a standard room air cleaner running all day uses approximately 394 kWh per year, about $71 at 18¢ per kWh, and that certified models are more than 50% more efficient, saving roughly $18 to $40 a year depending on size. The recurring cost is the filter. Look up the price and the replacement interval before you buy, and ask whether the maker sells the filter for years after the model is discontinued. The EPA says a dirty, overloaded filter will not work well, so replace it on schedule.

Placement and smart controls

1. Follow the manual for clearance from walls and furniture; blocked intakes reduce airflow.
2. Close the bedroom door and windows while it runs; a unit sized for the room cannot clean air from the rest of the house.
3. Choose auto mode if the unit has a particle sensor, but test how it behaves at night, since some ramp up for a moment when you move around.
4. A smart plug schedule only works if the unit restarts by itself when power returns. Many require a button press. Check before relying on it.

When a purifier is not the answer

If the problem is humidity or a musty smell, see smart humidity control. If the issue is smoke from a wildfire, read our wildfire smoke guide. For pollen season or dust, the allergy season air quality kit adds a monitor and filter plan. To decide between a portable unit and a furnace filter upgrade, read air purifier vs MERV 13 furnace filter.