Contra Wirecutter on the IKEA air purifier
I&#x27;m inclined to debunk this debunking. To be clear, I do think that Wirecutter has problems. I don&#x27;t like their practice of affiliate-linking. I think a review company should avoid even the &quot;appearance of evil&quot;. 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.<p>But I think this article, while it does present a lot of facts, is wrong about many of its conclusions.<p>On whether the IKEA purifier uses HEPA filters or not:<p>&gt; 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.<p>According to Wikipedia [1], &quot;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.&quot;<p>So that&#x27;s an &quot;H13&quot; or better to use the terminology of the article. (The H in the name literally indicates that it&#x27;s a <i>high efficiency</i>, or HEPA, filter.) The IKEA filter, according to the website, is a &quot;99.5%&quot; filter; they claim this &quot;corresponds&quot; to EPA 12, but Wirecutter&#x27;s test results (below) may cast doubt on this. (The author mocks Wirecutter for apparently not doing this &quot;research&quot;.) However, this just proves Wirecutter&#x27;s point: IKEA&#x27;s filters are not HEPA filters, and their pick&#x27;s filters are. Is this important? I don&#x27;t know, but score one for Wirecutter in getting the terminology right.<p>I&#x27;m not sure what Wirecutter is trying to say with the &quot;PM2.5&quot; 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 <i>does</i> 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.<p>I&#x27;m no expert in the physics of filters, and it sounds like this author is not either, but I&#x27;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 <i>remaining</i> particles - even though, over time, the particles that remain in the room are the particles that the filter had &quot;trouble&quot; catching on previous cycles. So you should expect to see reduced efficiency on later cycles, I would think.<p>Regardless, what would really help is if someone had done some testing in an actual room. Oh wait, you&#x27;re telling me Wirecutter did this??<p>&gt; 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.<p>So, even though nitpicks are in order, Wirecutter&#x27;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&#x27;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!)<p>&gt; 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.<p>Uh, sure. The reported result was &quot;CADR 56.3&quot; 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&#x27;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 &quot;PM2.5&quot; filter: <i>they are at or above their stated efficiency for 3 micron particles, and considerably below it for particles used in testing HEPA filters</i>. To my thinking that&#x27;s a very important fact that this article just glosses over.<p>At issue here is whether IKEA&#x27;s claimed 99.5% efficiency, which this article touts, is only true of PM2.5 or also true for 0.3 micron particles. IKEA&#x27;s product page is somewhat confusing and self-contradictory on this issue (which the article doesn&#x27;t point out), but Wirecutter&#x27;s test results would seem to cast doubt on the idea that the filter is 99.5% efficient by HEPA standards.<p>On costs: point taken, IKEA is cheaper <i>at the per-unit level</i>, 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).<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;HEPA" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;HEPA</a>