Why this site exists
The channel is about the gap between what a box promises and what a purifier does, and one promise comes up more than any other: the room size. Almost every purifier claims to clean a room several times bigger than it really can, because makers are free to choose how often the air gets changed, and they choose a very slow rate.
So we size every purifier the same way, at 4.8 air changes an hour, the rate AHAM's own room-size guideline uses. This site is that list: what each purifier really cleans and how often it needs a new filter. We put it here so you don't have to pause a video and read a spec sheet.
How we work, and what we don't do
We don't test purifiers. There's no lab and no smoke chamber, and we don't ask brands for review units. What we do is collect each model's published figures, check them against their sources and turn them into the number the box gets wrong: the room size it really cleans.
- Where the numbers come from. The smoke CADR comes from AHAM's Verifide directory, where an independent lab measures it and AHAM certifies the result: 17 of the 26 models we list. Everything else, and the CADR of the 9 models AHAM doesn't list, is the maker's own claim. Every figure is labelled with the kind of source it comes from.
- How picks are chosen. By the same written rules for every model: a certified CADR, enough for the room at 4.8 air changes an hour, with air to spare. The rules
- How figures are checked and corrected. Each figure shows its source and the date we last checked it. When a maker changes a spec or you spot a mistake, we fix it, change the date and say what changed in our next video.
- What we don't do. No hands-on tests, no paid placements, no prices.
How this site makes money
As an Amazon Associate I earn from qualifying purchases.
When you follow a link marked “Paid link” and buy something on Amazon, Amazon pays us a small commission. You pay the same price. That's the only way the site earns anything.
- Brands can't pay to be listed, ranked or picked, and the picks follow the same rules for every model.
- No sponsored posts, no ads, no affiliate links dressed up as anything else.
- We don't show prices: Amazon only allows prices taken live from its own systems, and they change daily.
Contact and corrections
Found a number that's wrong or out of date, or want a purifier added? Email hello@buybyspecs.tech. We fix mistakes, update the “checked on” date and mention the change in our next video.
How accurate this is
We check every figure against its source and show the date we checked it. Even so, makers change specs, filters and models without notice, and we make mistakes. Our size drawings use the makers' published dimensions and the makers' own product photos, which may show a different colour or a sister model.
We can't promise that everything on this site is complete, accurate or up to date. The BuyBySpecs Team isn't responsible for errors, omissions or out-of-date information, or for decisions made on them. Before you buy, check the figures that matter to you on the maker's own page.