Comment by addicted
3 years ago
This article actually makes a bunch of claims itself that are false. For example, it claims that the Wirecutter believes air filters work like sieves. Whereas the Wirecutter review page for air purifiers goes into how they do not behave like sieves and also references a NASA study that shows how HEPA filters are good at capturing both particles smaller and larger than the 0.3 micron test standard.
It’s pretty obvious that the Wirecutter has used HEPA standard filters as a filter for whittling down the many air purifiers that exist in the world. They eliminated the IKEA filters because they do not meet HEPA standards (this blog’s focus on he true-HEPA marketing term is misguided, because the authors own referenced wiki link shows that E12 is not considered HEPA). However, they also reached out to IKEA about this, and the IKEA spokesperson told them their focus is on PM2.5.
They don’t recommend the IKEA filter based not on its inability to capturer finer particles, but because it’s not AS efficient as capturing finer particles as HEPA filters, AND because of its lower CADR.
It doesn’t meet the standards they set, so they don’t include it for price comparisons.
Maybe they haven’t set the right standards. Maybe they should have allowed for lower CADRs or for filters that meet lower filtration standards than HEPA.
However, the insinuation this article makes that they don’t seem to understand what they’re talking about is completely wrong.
Maybe this author should try reviewing over 20-30+ different air purifiers at a minimum without setting arbitrary thresholds up front and then get back to the Wirecutter folks.
> HEPA filters are good at capturing both particles smaller and larger than the 0.3 micron test standard
That is due to MPPS - the only thing that matters is the actual reference particle size, not larger or smaller particles, as these are ultimately easier to filter. That is, particles between 0.2 and 0.3 microns are the most difficult to effectively filter out.
> their focus is on PM2.5
Which doesn't mean it doesn't trap 0.3 micron particles, as PM2.5 is Particulate Matter up to 2.5 microns in size, not 2.5 microns and up.
There are inconsistencies between their main air filter recommendation article and the specific review; if you haven't, read the article about the IKEA filter here: https://www.nytimes.com/wirecutter/blog/ikea-fornuftig-air-p...
The Wirecutter article is pretty bad though:
> But it isn’t a true-HEPA purifier, or a very powerful purifier, period. It’s designed to capture PM2.5—that is, particles 2.5 microns in diameter and above, in contrast to the 0.3-micron HEPA standard. That means it’s optimized for larger airborne particles such as pollen and mold spores, rather than for very fine particulates like wildfire smoke, as HEPA filters are.
First, "True-HEPA" has no legal or scientific meaning, so that's not a great look.
Second, and a minor point, the 0.3-micron standard related to the US HEPA standard, not the EU one. It is true that acording to IKEA it doesn't meet the EU standard for HEPA (barely), but we don't know whether it meets the US one. Eliding the difference between different standards isn't helpful
Third, and more seriously, PM2.5 means particles 2.5 microns in diameter and smaller, not larger, and PM2.5 filters are designed to capture particles 2.5 microns and smaller. Mold spores are mostly 4 to 20 microns, pollen averages around 25 microns, so while the IKEA unit may or may not be good at filtering wildfire smoke, it is not optimised for mold and pollen and is probably terrible at it, so that entire line of analysis is just backwards.
That's a lot of errors to pack into a short passage, and it really gives the impression that the author doesn't really understand or care about the topic.
As for CADRs, the linked post digs into the tests pretty well, and I agree with the conclusion - they're not credible. Note specifically that they get a variance of over 2.4 times between tests, and in somes cases measure a CADR vastly higher than the manufacturers claimed CADR. If you're reading a benchmark of a new graphics card and someone ran a benchmark twice and got 100 FPS once and 240 FPS the second time, and they just shrug and pick the number most convenient for their conclusion, you'd probably think something was up.
(That being said, the linked post is a bit iffy too. I'd call out specifically that they could have done a better job of acknowledging that US HEPA standards are a thing, that PM2.5 filters are a thing even if they're not a standard, and that technically E12 filters aren't HEPA, even if that's an arbitrary distinction most people ignore. But they're quite right that the Wirecutter - on the review of the IKEA unit - does in fact seem to think air filters work like sieves. Certainly I can't think of any other explanation for that passage about PM2.5 being good for pollen!)
> Second, and a minor point, the 0.3-micron standard related to the US HEPA standard, not the EU one. It is true that acording to IKEA it doesn't meet the EU standard for HEPA (barely), but we don't know whether it meets the US one.
Wikipedia cites this statement:
> Common standards require that a HEPA air filter must remove—from the air that passes through—at least 99.95% (ISO, European Standard) [...] of particles whose diameter is equal to 0.3 μm
to "European Standard EN 1822-1:2009, "High efficiency air filters (EPA, HEPA and ULPA)", 2009". Have they made a mistake? ( https://en.wikipedia.org/wiki/HEPA )
The same sentence goes on to note that the American standard is similar, but more strict, requiring filtration of 99.97% of 0.3 μm particles. As such, it is not possible to meet the American standard while failing to meet the European standard, so there's no need to discuss the American standard separately.
From the same Wikipedia page:
> The specification used in the European Union: European Standard EN 1822-1:2009, from which ISO 29463 is derived,[4] defines several classes of filters by their retention at the given most penetrating particle size (MPPS): Efficient Particulate Air filters (EPA), HEPA and Ultra Low Particulate Air filters (ULPA).
The Wikipedia citation goes to a specification which is, annoyingly, not freely available, but Google seems to confirm that Wikipedia is correct. Many sources confirm that EU standards measure penetration at the MPPS, I can find nothing suggesting they use 0.3 microns for anything.
I think the introduction paragraph for that Wikipedia page is simply wrong, and it's conflating two different standards. The actual section on HEPA specifications, however, is much clearer.
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> This article actually makes a bunch of claims itself that are false.
There's this howler:
> This passage implies that a (“true”?) HEPA filter is designed to capture particles that are 0.3 microns or larger. But an H13 filter must, by definition, capture 99.95% of particles of all sizes.
According to this guy, an H13 filter is required to capture 99.95% of neutrinos that pass through it. He's not in a position to accuse anyone of not knowing what they're talking about.
Moving to wikipedia, we see this text:
> 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
I know which of those claims is more plausible. The standard described by wikipedia is theoretically capable of both being measured and being met. Neither is true of what dynomight.net says.
You cannot possibly be serious.
If you are, well, you will find that particles are contextually defined as pieces of matter in the solid or liquid phase which are suspended in the air.
I don't know if the standards body took pains to define matter in terms of atoms but if you want to run off and check? I won't stop you.
He's just honing his HN pedantry to a razor edge so he can point out that ackshewally it's not an air filter at all because it isn't restricted to gaseous fluids in the ratio of 0.78 oxygen to 0.21 nitrogen plus trace gases.
It can actually filter many types of gaseous compositions so it's really a gas filter. Have the authors even done a rudimentary PhD on filtration nomenclature? They are clearly unqualified to comment.
Seriously though I've seen enough of these sorts of Poe's that at least some of them must be serious. Must be weird living your life like that.
> you will find that particles are contextually defined as pieces of matter in the solid or liquid phase which are suspended in the air.
What is this supposed to mean? The solid or liquid phase is defined by the interaction of related molecules with each other. Suppose I have a cluster of 15 water molecules, suspended in the air, interacting with each other such that I can call them a tiny droplet of liquid water. Suppose I have one oil molecule, also suspended in the air. It is much larger than the 15 water molecules are combined. But it's not in a solid or liquid phase, because there's only one of it. The filter is required to handle the water, but there are no requirements for how it should handle the oil?
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