Start with room size and usable airflow, then compare filter care, controls and ownership costs.

Research updated 4 October 2026 · US edition

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01Measure one room, including ceiling height

Multiply length by width to find floor area. Compare the room with a rating that states its air changes per hour (ACH). AHAM’s room-size benchmark uses 4.8 ACH; an advertisement for one air change per hour describes a much slower cleaning rate. Our comparison shows manufacturers’ 4.8-ACH room figures rather than their larger one-hour headlines.

02Understand what CADR measures

Clean air delivery rate (CADR) describes the amount of particle-cleaned air supplied over time. Compare the same particle category and units where possible. As a transparent sizing estimate, room area in square feet = CADR in cubic feet per minute × 60 ÷ ceiling height in feet ÷ target equivalent air changes per hour. For example, 200 cfm with an 8-foot ceiling at 4.8 equivalent changes gives about 313 square feet. This calculation is not a guarantee about a real room or a health outcome.

03Choose a fan speed you will actually use

Maximum airflow and minimum noise normally describe different settings. If you need quiet operation overnight, look for independent measurements at the quieter setting. Lower airflow means less room coverage at the same cleaning rate. Manufacturer dB claims and different reviewers’ sound measurements are not directly interchangeable.

04Check filters before buying the purifier

Find the exact replacement filter and confirm US availability. A washable pre-filter does not mean the main particle filter is washable. Follow the manual’s care instructions. To estimate yearly filter cost, multiply a filter’s current price by the expected number of changes; describe the interval as an assumption, not a guaranteed lifespan. Special-purpose filters may have different costs and airflow.

05Keep electricity estimates transparent

Annual electricity cost = operating watts ÷ 1,000 × hours per day × 365 × your electricity tariff. As an illustration, 20 watts for 12 hours daily at $0.15 per kWh is about $13.14 a year. Those are example inputs, not measured costs for any product here. Rated maximum power is not necessarily everyday consumption.

06Decide whether you need smart controls

On-device controls are enough for many routines. Apps add scheduling and remote adjustment. Auto mode responds to the built-in sensor; it does not measure every pollutant or prove that the room is safe. In this shortlist, Coway’s original Mighty is the option without an app; the other four offer connected controls.

07Distinguish particles, gases and filtration methods

A high particle CADR does not establish strong gas or odor removal. Carbon type and quantity matter, and a purifier does not replace controlling pollution sources or appropriate ventilation. Some designs add electrostatic filtration or an ionizer. Check whether that stage can be disabled if that matters to you; do not treat filtration as a promise to prevent or treat illness.

08Place it well and compare the exact offer

Leave inlet and outlet clearance according to the manual rather than hiding the purifier behind furniture. Confirm the US model, included filter and delivery availability. The Blueair shop also offers a filter subscription: choose purifier-only if you do not want recurring deliveries. The original Coway Mighty is different from Mighty2, and Winix 5510 is different from 5500-2. The Levoit Vital 200S-P offer also needs an exact model-label and replacement-filter check; its tested 200S family sample is not proven identical.

Sources behind this guide +

• AHAM — room size and air changes per hour
• EPA — guide to air cleaners in the home
• HouseFresh — quiet-speed and full-speed testing