Buy the Levoit Core 600S unless chemical odors or VOCs are a real problem in a room larger than about 600 sq ft. The AirDoctor AD5500i moves about 42% more air (556 vs 391 CFM) and has a far heavier gas stage, but its filters cost about $355 a year against $60, so it costs roughly four times as much to own over three years.
The short answer
Choose the Core 600S if the room is up to about 600 sq ft, your concern is particles (dust, pollen, pet dander, wildfire smoke), and you want big-room cleaning for a total cost near $420 over three years.
Choose the AD5500i if the space is 600 to 860 sq ft, or you are dealing with off-gassing, chemical sensitivity or persistent smoke odor, and the filter bill of about $355 a year is acceptable.
| On paper | AirDoctor AD5500i | Levoit Core 600S |
|---|---|---|
| Smoke CADR | 556 CFM (AirDoctor's figure) | 391 CFM (AHAM rating, current 600S-P) |
| Room size at 4.8 air changes/hr | ~862 sq ft | ~606 sq ft |
| Rated noise | 30 to 50 dB | 26 to 55 dB |
| Rated maximum draw | 110 W | 49 W |
| Filters | 2 UltraHEPA (12 mo) + 2 Carbon/VOC (6 mo) | One combined cylinder, $59.99 |
| One year of genuine filters | $354.99 combo pack | ~$60 |
| App and auto mode | Yes | Yes |
| Typical price | $999 list at AirDoctor, often discounted | $280–$320 |
The brand-level matchup against Coway is covered in AirDoctor vs Coway. This page is specific to the AD5500i and the Core 600S.
How big a room each one handles
Air changes an hour equal CADR times 60, divided by room volume. With 8 ft ceilings and both units at full speed:
| Room | AD5500i | Core 600S |
|---|---|---|
| 18 x 25 family room (450 sq ft) | 9.3 changes/hr | 6.5 changes/hr |
| 24 x 28 open plan (672 sq ft) | 6.2 | 4.4, short |
| 26 x 33 great room (858 sq ft) | 4.9, at its limit | 3.4 |
| 30 x 35 loft (1,050 sq ft) | 4.0, short | 2.8 |
Up to about 600 sq ft the Levoit is enough and the AirDoctor is simply faster. Between 600 and 860 sq ft only the AirDoctor reaches 4.8 changes an hour by itself. Taller ceilings shrink both: at 9 ft, the limits drop to about 766 and 539 sq ft. AirDoctor's own 1,043 sq ft figure assumes four air changes an hour, which is gentler than the standard used here. Check your space with the room size calculator.
What the extra money buys: the gas stage
The AirDoctor's real difference is not airflow, it is chemistry. Each side of the AD5500i carries a separate Carbon/Gas Trap/VOC filter, and AirDoctor says that carbon is enhanced with potassium permanganate, which reacts with gases such as formaldehyde rather than only holding them. Those filters are swapped every six months, so the gas stage is refreshed twice a year.
The Core 600S puts its pre-filter, HEPA media and carbon into one cylinder. That handles everyday cooking smells and pet odor, but there is far less carbon for a smell that keeps coming back. Levoit's Toxin Absorber ($69.99) and Smoke Remover ($79.99) cylinders help, at a small premium per swap.
So the question is what you are fighting. Fresh paint, a new sofa, a renovated room or a neighbor's smoke seeping through the walls: the AirDoctor's gas stage is the reason to pay more. Pollen, dust and dander: the Levoit catches those just as well for a fraction of the cost. The best purifiers for VOCs page ranks the options when gases are the main issue.
Three-year cost
Assumptions: AD5500i at its $999 list (sales vary too much to bank on); Core 600S at about $300; first filters in the box; AirDoctor's 1-year combo pack at $354.99 each year after the first; the 600S cylinder replaced yearly per the site's catalog; electricity at $0.17/kWh.
| Over 36 months | AD5500i | Core 600S | Two Core 600S |
|---|---|---|---|
| Purchase | $999 | ~$300 | ~$600 |
| Filters | 2 x $354.99 = ~$710 | 2 x $59.99 = ~$120 | ~$240 |
| Total before power | ~$1,709 | ~$420 | ~$840 |
| Combined smoke CADR | 556 CFM | 391 CFM | 782 CFM |
| Power ceiling (max draw, 24/7) | ~$164 a year | ~$73 a year | ~$146 a year |
Buying the AirDoctor's filters individually costs more, not less: two UltraHEPA filters at $133 plus two pairs of Carbon/VOC filters at $131 come to $395 a year. The power row is an upper bound, since neither maker publishes low-speed draw. Even if the 600S needs a fresh cylinder every seven months, the single Levoit's total comes to about $600.
The third column is the point. Two Core 600S units, one at each end of a long open space or one in the living room and one in the bedroom, deliver more combined airflow than one AD5500i for about half the three-year cost. What they cannot match is the gas stage.
Noise, power and day-to-day details
Quiet floor. The Core 600S is rated down to 26 dB, the AD5500i to 30 dB. In a bedroom the Levoit is the softer of the two at its lowest setting. At the top end the AirDoctor is rated quieter, 50 dB against 55.
Power draw. At 110 W maximum, the AirDoctor uses more than twice the Levoit's 49 W ceiling. It also moves more air, so per CFM the gap is smaller than it looks.
Auto mode. Levoit says the 600S-P's auto mode won't use its high or turbo speeds, so for a smoke event switch to a manual speed. Both units have sensors, apps and schedules.
Rating source. The Core 600S's 391 CFM is an AHAM rating; the AD5500i's 556 CFM is AirDoctor's published number, with no AHAM Verifide listing found. That doesn't make the AirDoctor's figure wrong, but it is the less independently checked of the two.
Which one to buy
For a typical living room, bedroom or basement up to 600 sq ft with particle problems, buy the Levoit Core 600S. For two separate problem areas, two of them still cost less than one AirDoctor. Buy the AirDoctor AD5500i when the space is genuinely 600 to 860 sq ft open plan, or when gases and odors are the reason you are shopping, and budget about $355 a year for filters before you order.
If a Coway is on your shortlist, the Coway Airmega 400 vs Core 600S comparison covers the middle ground. For heavy chemical sensitivity with no budget ceiling, the IQAir HealthPro Plus is the step beyond both, and IQAir vs AirDoctor weighs it against the AD5500i.
Frequently asked questions
How often do AirDoctor AD5500i filters need replacing?
AirDoctor's help center gives 12 months for the UltraHEPA filters and 6 months for the Carbon/Gas Trap/VOC filters on the 5000 series, which includes the AD5500i. The pre-filters are permanent and only need vacuuming. That schedule is why the one-year combo pack holds two UltraHEPA and four carbon filters.
Is the AirDoctor's 556 CFM rating AHAM-verified?
No AHAM Verifide listing for the AD5500i turned up in research, so 556 CFM is AirDoctor's own figure. The Core 600S's 391 CFM is an AHAM rating. Treat the AirDoctor's number as a manufacturer claim when comparing.
Can the Core 600S handle VOCs from new flooring or paint?
Only modestly with the standard cylinder. Levoit's Toxin Absorber cylinder for the 600S-P, at $69.99, puts more emphasis on gases, but it is still one combined filter. For ongoing chemical off-gassing in a big room, the AirDoctor's separate carbon filters with potassium permanganate are the stronger tool.
Do both purifiers have an app?
Yes. The AD5500i connects to AirDoctor's app and the Core 600S to Levoit's VeSync app, and both have auto modes driven by an air-quality sensor. Neither app is a reason to pick one over the other.
Is the AD5500i overkill for a 300 sq ft bedroom?
On airflow, yes. At full speed it would give a 15 x 20 ft room about 14 air changes an hour, nearly three times the 4.8 this site sizes for. It only makes sense there if the bedroom has a chemical-odor problem; for particles alone, a Core 600S or even a Levoit Core 400S-P is plenty.