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Levoit vs AirDoctor: which air purifier should you buy?

The Levoit Core 600S vs the AirDoctor AD3500, compared on verified CADR, room size, filters and features, plus the right pick for smaller rooms.

Updated November 2026How we compared

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The short answer

For most homes, buy the Levoit Core 600S. Its smoke CADR is higher than the AirDoctor AD3500's (410 vs 336 CFM), so it clears a large room faster. It adds the VeSync app, and it sits in a lower price tier.

Buy the AirDoctor AD3500 if odors are your main problem — cooking, pets or smoke. It gives odors a separate, dedicated carbon/VOC filter.

Levoit Core 600S on Amazon AirDoctor AD3500 on Amazon

Head to head

	Levoit Core 600S	AirDoctor AD3500
Smoke CADR	410 CFM	336 CFM
Room size at about 5 air changes per hour*	about 640 sq ft	about 525 sq ft
Listing claim (1 air change per hour)	up to 2,933 sq ft	up to 2,520 sq ft
Filters	One 3-in-1 cartridge: pre-filter, H13 True HEPA, activated carbon	UltraHEPA filter plus a separate carbon/VOC filter
App and Wi-Fi	VeSync app, Alexa	None (the AD3500i version adds an app)
Auto mode and air sensor	Yes	Yes
Weight	13.7 lb	18 lb
Warranty	2 years	1 year
Price tier	Mid-range	Premium

*Calculated the same way for both: 4.8 air changes an hour in a room with 8 ft ceilings. Brands often quote far bigger numbers based on just one or two air changes an hour.

What the differences mean

Cleaning speed: Levoit wins

CADR (Clean Air Delivery Rate) measures how much filtered air a purifier delivers per minute, and it's the best single number for comparing purifiers. Independent testing points the same way. In HouseFresh's tests, the Core 600S reached about 375 CFM at top speed, versus about 299 CFM for the AirDoctor AD3000, which AirDoctor's lab report says performs the same as the AD3500. The Levoit simply moves more clean air.

The “100x smaller than HEPA” claim

AirDoctor markets its UltraHEPA filter as capturing particles down to 0.003 microns, 100 times smaller than the HEPA standard. The catch: HEPA is rated at 0.3 microns because that's the hardest size to trap, not the smallest it can trap. According to the EPA, particles larger and smaller than 0.3 microns are captured even more efficiently. In a real room, airflow through the filter matters more than the 0.003-micron claim.

Odors and VOCs: AirDoctor's edge

AirDoctor keeps its carbon/VOC filter separate from the particle filter, so you can replace either one on its own; HouseFresh singled this out as a plus. The Core 600S uses one bonded cartridge, so when the carbon is spent you replace the whole thing, even if the HEPA layer still has life left.

Smart features

The Core 600S works with the VeSync app and Alexa, with schedules and customizable auto modes. The standard AD3500 has auto mode and an air quality light but no app; AirDoctor sells the AD3500i if you want Wi-Fi.

Which one should you buy?

Buy the Levoit Core 600S if

Large or open-plan rooms
You want the most cleaning speed for the money
You want app control, schedules or Alexa

Check price on Amazon

Buy the AirDoctor AD3500 if

Odors from cooking, pets or smoke are the main problem
You want an odor filter you can replace separately
You don't need an app (or buy the AD3500i)

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For a bedroom or a room under about 400 sq ft

Skip both. The Levoit Core 400S (260 CFM) and the Levoit Vital 200S (about 245 CFM) are sized for rooms up to roughly 400 sq ft. AirDoctor's small-room model, the AD1000, is rated for about 285 sq ft.

Levoit Core 400S on Amazon Levoit Vital 200S on Amazon

Questions people ask

Is AirDoctor better than Levoit?

Not for most homes. The Levoit Core 600S has a higher rated CADR than the AirDoctor AD3500 (410 vs 336 CFM for smoke), so it cleans a large room faster. It also adds app control and sits in a lower price tier. AirDoctor's real advantage is a separate, dedicated carbon/VOC filter for odors.

Does AirDoctor really filter particles 100x smaller than HEPA?

AirDoctor says its UltraHEPA filter captures particles down to 0.003 microns. But the 0.3-micron figure in the HEPA standard is the hardest particle size to catch, not the smallest: according to the EPA, HEPA filters trap particles both larger and smaller than 0.3 microns even more efficiently. In a real room, how much air a purifier pushes through its filter (its CADR) matters more than the 0.003-micron claim.

Which is better for smoke?

For smoke particles, the Levoit Core 600S: its smoke CADR is 410 CFM versus 336 CFM for the AirDoctor AD3500, so it clears them faster. For lingering smoke odor, the AirDoctor's separate carbon/VOC filter is the better tool.

Which should I buy for a bedroom?

Neither of these. For rooms under about 400 sq ft, the Levoit Core 400S (260 CFM) or Levoit Vital 200S (about 245 CFM) is the right size. AirDoctor's small-room model, the AD1000, is rated for about 285 sq ft.