I'm inclined to debunk this debunking. To be clear, I do think that Wirecutter has problems. I don't like their practice of affiliate-linking. I think a review company should avoid even the "appearance of evil". But more importantly, their practices seem spotty: they tend to test only a relatively small number of models, which may not accurately reflect the market.

But I think this article, while it does present a lot of facts, is wrong about many of its conclusions.

On whether the IKEA purifier uses HEPA filters or not:

> They make a big deal about this, which is weird since “true-HEPA” has no legal or scientific meaning. Meanwhile, they refer to the IKEA purifier as using a “PM2.5 filter” which also isn’t a thing.

According to Wikipedia [1], "Common standards require that a HEPA air filter must remove—from the air that passes through—at least 99.95% (ISO, European Standard) or 99.97% (ASME, U.S. DOE) of particles whose diameter is equal to 0.3 μm, with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 μm."

So that's an "H13" or better to use the terminology of the article. (The H in the name literally indicates that it's a high efficiency, or HEPA, filter.) The IKEA filter, according to the website, is a "99.5%" filter; they claim this "corresponds" to EPA 12, but Wirecutter's test results (below) may cast doubt on this. (The author mocks Wirecutter for apparently not doing this "research".) However, this just proves Wirecutter's point: IKEA's filters are not HEPA filters, and their pick's filters are. Is this important? I don't know, but score one for Wirecutter in getting the terminology right.

I'm not sure what Wirecutter is trying to say with the "PM2.5" language, but they may be trying to get across to consumers that these filters are more akin to a typical filter that you would get for your residential air conditioning unit. Notably, such filters are often categorized on the MERV scale, which does use minimum particle size effectively handled by the filter as a metric. Regardless, Wirecutter is somewhere between lazy and misleading on this, and the article is right to point this out.

I'm no expert in the physics of filters, and it sounds like this author is not either, but I'm a little skeptical that repeated applications of a lower efficiency filter are just as good as applications of a higher efficiency filter. Their charts rest on the assumption that every pass, a HEPA filter will remove 99.95% of remaining particles - even though, over time, the particles that remain in the room are the particles that the filter had "trouble" catching on previous cycles. So you should expect to see reduced efficiency on later cycles, I would think.

Regardless, what would really help is if someone had done some testing in an actual room. Oh wait, you're telling me Wirecutter did this??

> Even if we accepted all these test results (we don’t) that would just show the Wirecutter pick provides around 3.3 times as much cleaning per second.

So, even though nitpicks are in order, Wirecutter's pick costing $100 vs the $70 IKEA will clean the air 3.3 times as efficiently?? That seems like a good deal. Even if it uses more electricity and more expensive filters, I'm not going to want to purchase 3 units when 1 will do. (This efficiency difference will obviously extend to large rooms in the same way!)

> IKEA claims a CADR of 82.4 on high, and 53.0 on medium. So even taken at face value, this says that IKEA performs a bit above spec on 3.0-micron particles and a bit below spec on 0.3-micron particles.

Uh, sure. The reported result was "CADR 56.3" for 0.3 micron particles on high. Notably, 0.3 microns is supposed to be the low point for filters tested according to the standards used for HEPA. So it's worrying to see IKEA underperform the stated efficiency by this much at exactly the particle size we most care about when testing for HEPA. If I had to guess, this is probably why Wirecutter calls the IKEA filter a "PM2.5" filter: they are at or above their stated efficiency for 3 micron particles, and considerably below it for particles used in testing HEPA filters. To my thinking that's a very important fact that this article just glosses over.

At issue here is whether IKEA's claimed 99.5% efficiency, which this article touts, is only true of PM2.5 or also true for 0.3 micron particles. IKEA's product page is somewhat confusing and self-contradictory on this issue (which the article doesn't point out), but Wirecutter's test results would seem to cast doubt on the idea that the filter is 99.5% efficient by HEPA standards.

On costs: point taken, IKEA is cheaper at the per-unit level, both at point of purchase and throughout its lifespan. But given the apparent efficiency differences, discussed above, I think someone going with the Wirecutter pick is not completely unreasonable. If you want to dispute this result, I think the only way to do that is to do your own testing (which this article does not do).

[1] https://en.wikipedia.org/wiki/HEPA