Guides
Practical buying guides for air purifiers ā spec math, filter economics, and what the marketing doesn't tell you.
GuideCADR is the only number that matters, and 'HEPA' is the most abused word in the categoryAir purifier marketing buries you in claims ā HEPA, ionizers, room sizes, percentages. One real spec tells you whether a unit actually cleans your air at a uā¦GuideWhere to Put an Air Purifier (and the Placement Mistakes That Waste Its CADR)You can buy enough clean-air delivery and still throw half of it away with bad placement. Why airflow is the whole game, the placement mistakes that choke a ā¦GuideTrue HEPA vs 'HEPA-Type': The One Word That Changes the Filter'True HEPA' meets a defined filtration standard. 'HEPA-type', 'HEPA-like', and '99%' are marketing words that don't ā and let through far more of the small pā¦
Buying guide
How to choose an air purifier: true HEPA, CADR, and room size
True HEPA vs HEPA-type, CADR ratings that match your room, filter replacement costs per year, and noise levels that won't disturb sleep. The complete spec breakdown.
Why this page exists
Air purifier marketing is among the most misleading in home appliances. "HEPA-type" filters that capture far fewer particles than true HEPA. CADR numbers listed for a room size your unit can't handle. Filter subscription costs that exceed the price of the unit within two years.
The spec that matters most ā CADR ā is buried in footnotes, while "clean air" promises fill the front page. This guide teaches you to read the actual numbers so you can compare units honestly.
Plain note about money. Links below go to eBay searches with an affiliate tag. If you buy through one, a small commission comes to this site. Your price is identical either way. The searches are ones we'd actually run ā not sponsored placements.
Air purifiers worth searching on eBay
True HEPA and high-CADR units across room sizes and use cases. We earn a small commission on qualifying sales; your price is unchanged. Full disclosure.
HEPA Air Purifier
True H13 HEPA filtration captures 99.97% of particles 0.3 microns and larger. The baseline spec to look for before comparing anything else.
Air Purifier for Large Rooms
Units with CADR 200+ CFM rated for 400ā600 sq ft spaces. Higher CADR costs more upfront but achieves more air changes per hour where it counts.
True HEPA Filter Replacement
Replacement filters are often the hidden long-term cost. Compatible aftermarket filters can cut annual running costs significantly versus OEM pricing.
Air Purifier for Bedroom
Bedroom units prioritize noise ā look for 35 dB or under on the lowest fan setting. Sleep mode and auto-dimming displays matter more here than raw CADR.
Air Purifier for Pets
Pet dander and odors require both HEPA and activated carbon filtration. Look for units with substantial carbon weight ā thin carbon mats exhaust quickly.