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Contra Wirecutter on the IKEA air purifier

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Re: Contra Wirecutter on the IKEA air purifier

#701

Post by weaksauce »

highwaylights wrote: post #342
weaksauce wrote: post #257

Earlier quoted context omitted.

> Almost all of these review sites, not understanding the physics involved, believe a HEPA filter sieves particles down to a size of 0.3 microns, which implies that anything smaller passes on through. To be fair, it took a pandemic for me to go to the literature of mask effectiveness and finally found the "on the filtration efficiency of fiberous filters" paper that showed the u shaped curve. it's not something that…

You might also enjoy this: https://www.youtube.com/watch?v=cagRuiyAsio

that's a president really standing by their product... impressive.

Re: Contra Wirecutter on the IKEA air purifier

#702

Post by amluto »

etchalon wrote: post #696
amluto wrote: post #688

Earlier quoted context omitted.

Extraordinary claims require extraordinary evidence. The data shows a huge difference which cannot be explained by the difference between 5 particles and 0.5 particles. As noted in the article, the Wirecutter does not explain its methodology or give particularly complete data, and what explanations they do give about filtration make no sense.

It's a 10x difference in filtration efficiency, combined with a CADR difference between the two units. I don't understand why you think more of an explanation is required?

There is a 10x difference between (1-efficiency) for the two filter media choices. Explanation needed as to why this is at all relevant.

Your comment is like observing that car A burns 87 octane gasoline and another burns 89 octane gasoline and claiming, without explanation, that one of them accelerates faster because (90-octane) is 3x lower.

hint: the bigger purifier wins because it has a more powerful, more power hungry fan pushing air through it. Its performance might be further improved (depending on the fan and motor characteristics) by putting a less efficient, lower pressure drop filter in because more air would go through it per unit time.

Meanwhile, two IKEA filters will outperform it in every measure, including cost, noise, and power consumption. But their efficiency will still be lower.

Re: Contra Wirecutter on the IKEA air purifier

#703

Post by weaksauce »

etchalon wrote: post #307
weaksauce wrote: post #260

Earlier quoted context omitted.

> The idea that the difference between 0.9005 and 0.90005 is "small" is … weird. it is. that's one minute of filtration and the difference is minuscule. over time, this would trend to zero. in 10 minutes you'd expect to be near the steady state of the room. (obviously not completely steady state since you are filtering some already filtered air and probably introducing more particulates but close enough for an approx…

It's a 10x difference. It's not small. In a sealed environment, you're right, you'd eventually end up with all particles filtered. But homes are not sealed environments.

in practice the filtration in a room goes down exponentially and quite quickly even with budget filters that only filter out 90%. even in shops where you are sanding.

https://woodgears.ca/dust/dylos.html

Re: Contra Wirecutter on the IKEA air purifier

#704

Post by sixothree »

GekkePrutser wrote: post #670
sixothree wrote: post #666

Earlier quoted context omitted.

Got a link to DisplayCheck? I'm not finding what I think should be correct.

Sorry I remembered it wrong. It was DisplayMate, not DisplayCheck. https://www.displaymate.com/mobile.html#Latest Their display "shootouts" are unparallelled in my opinion. For example they look at colour accuracy not only at high brightness but also at really low brightness, where displays often 'cheat' by reducing the contrast when they reach the limit of their backlight dimming. Which significantly impacts colour…

Thank you for the link. And there is no reason to apologize. You are not incorrect in your interpretation. I subscribe to LTT on YouTube, but it's for entertainment.

Re: Contra Wirecutter on the IKEA air purifier

#705

Post by asojfdowgh »

jefftk wrote: post #690
asojfdowgh wrote: post #686

Earlier quoted context omitted.

I really don't like this math, no one actually stops at that point, you take the output, la, "0.9005" and re-run it (0.9005 × .1) × (1-.995) + (0.9005 × .9) and again, and again, etc, point being that over time it does cycle the entire room, due to entropy, and then suddenly the differences start to stack up a bit, not a lot, but when one filter is letting 10x the particles through vs the other filter, it'll show

> suddenly the differences start to stack up a bit, not a lot, but when one filter is letting 10x the particles through vs the other filter, it'll show It doesn't show: the difference is too small to notice at every stage: https://www.jefftk.com/remaining-particles-by-minute-995-vs-... Even comparing 95% vs 99.95% it's barely noticeable: https://www.jefftk.com/remaining-particles-by-minute-95-vs-9... Sheet: https://d…

fair

Re: Contra Wirecutter on the IKEA air purifier

#706

Post by etchalon »

jefftk wrote: post #700
etchalon wrote: post #697

Earlier quoted context omitted.

The 70% and 99.95% difference is because of the 10x filtration efficiency difference, combined with the CADR difference. This is very straight-forward.

The "10x" you've been referring to is about the difference in how many particles make it through filters of 99.5% vs 99.95% efficacy [1], not 70% vs 99.95%, which would be 600x [2]. [1] (1−.995)÷(1−.9995) [2] (1−.7)÷(1−.9995)

"CADR" is a word I included for a reason.

Re: Contra Wirecutter on the IKEA air purifier

#707

Post by thaumasiotes »

samatman wrote: post #665
thaumasiotes wrote: post #562

Earlier quoted context omitted.

> 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 ac…

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.

> 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?

Re: Contra Wirecutter on the IKEA air purifier

#708

Post by notoriousjpg »

joshstrange wrote: post #28

Wirecutter has gone to shit and stopped being useful about 3-4 years ago. Their move to a paid subscription was very odd to me because they had also lost all my trust by that point. There are countless examples of recommends products doing a bait and switch (changing the materials/product after the wirecutter article recommending them came out) and just cases of Wirecutter giving bad recommendations.

surely moving away from being ad or affiliate driven would create more trust?

Re: Contra Wirecutter on the IKEA air purifier

#709

Post by Lazare »

thaumasiotes wrote: post #623
Lazare wrote: post #569

Earlier quoted context omitted.

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 f…

Technically, if retention at the most penetrating particle size is 99.95%, then retention at the 0.3 micron level is at least 99.95%. But obviously measurement is not actually done at the most penetrating particle size, because retention at that size would be indistinguishable from zero. It isn't clear what they mean when they say "most penetrating particle size". > defines several classes of filters by their retenti…

> But obviously measurement is not actually done at the most penetrating particle size, because retention at that size would be indistinguishable from zero. [...] If the MPPS is given... what is it?

I'm not entirely sure what you mean. Retention is a U shaped curve, with the local minima (aka the MPPS) around (as near as I can google), the 0.2 to 0.3 micron range. As a practical matter, because the MPPS seems to not vary much between filters, and is always quite close (although apparently always slightly smaller than the 0.3 micron US standard?) nobody really seems to stress about the exact MPPS size, and it doesn't seem to ever really be reported.

(Implicitly this entire discussion is taking place in the context of airborne particulates. Obviouslly no air filter is going to work very well against, say, gamma radiation. Or a car.)

Which does mean it is possible that you could have a filter that doesn't qualify as HEPA under the EU standard if, say, it hits 99.94% at a MPPS of 0.2 microns, but does qualify as HEPA under the US standard (if it hits 99.97% at 0.3 microns). Or conversely, it could hit 99.95% at an MPPS of 0.25 microns (thus being HEPA by the EU standard), but only 99.96% at 0.3 microns (thus not being HEPA by the US standard).

Which is interesting, except when you calculate the math as applied to actually filtering room air, they're all going to be effectively identical.

Re: Contra Wirecutter on the IKEA air purifier

#710

Post by thaumasiotes »

Lazare wrote: post #709
thaumasiotes wrote: post #623

Earlier quoted context omitted.

Technically, if retention at the most penetrating particle size is 99.95%, then retention at the 0.3 micron level is at least 99.95%. But obviously measurement is not actually done at the most penetrating particle size, because retention at that size would be indistinguishable from zero. It isn't clear what they mean when they say "most penetrating particle size". > defines several classes of filters by their retenti…

> But obviously measurement is not actually done at the most penetrating particle size, because retention at that size would be indistinguishable from zero. [...] If the MPPS is given... what is it? I'm not entirely sure what you mean. Retention is a U shaped curve, with the local minima (aka the MPPS) around (as near as I can google), the 0.2 to 0.3 micron range. As a practical matter, because the MPPS seems to not…

> Implicitly this entire discussion is taking place in the context of airborne particulates. Obviously no air filter is going to work very well against, say, gamma radiation.

I'm perfectly willing to consider gamma radiation "not particulate". But if we restrict ourselves to considering particles that have mass, the retention rate at the MPPS of any usable air filter is still going to be zero. The diameter of a water molecule is 0.000265 μm. This is significantly smaller than the diameter of an oxygen molecule at 0.000346 μm. Of course, I don't expect an air filter to remove 99.95% of the oxygen in the air. But I do expect the fact that oxygen molecules are airborne particles to be taken into account when we talk about the retention rate of airborne particles. Another commenter has stated that "particles" must be identifiably liquid or solid, but you can easily have an ice crystal of 20 molecules, which -- if it were a straight line measured along its length -- would still have a "diameter" of less than 0.01 μm.

So I don't understand how appealing to "but we're only talking about particles" is supposed to save this. Particles are, at their lower reaches, very small, much too small for an air filter to address without killing the user. It seems clear to me that any workable filter standard must define a minimum particle size below which filtration is neither measured nor desired. What is that size, for European filters?

>> But obviously measurement is not actually done at the most penetrating particle size, because retention at that size would be indistinguishable from zero. [...] If the MPPS is given... what is it?

Something's gone wrong... you've run together two completely separate comments as if they were related to each other.

>>> If the MPPS is given... what is it?

You quoted a standard that specifies a certain level of retention "at the given Most Penetrating Particle Size".

That wording explicitly states that the Most Penetrating Particle Size is defined by the standard ("given"). So, what is the MPPS?

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