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Contra Wirecutter on the IKEA air purifier

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Re: Contra Wirecutter on the IKEA air purifier

#691

Post by aidenn0 »

etchalon wrote: post #134
jefftk wrote: post #48

Earlier quoted context omitted.

The article explains it well: Here’s a thought experiment: Take a 1000 cubic feet room and a purifier that processes 100 cubic feet of air per minute. (I follow Wirecutter in using vulgar imperial units.) Assume pessimistically that all particles are the worst-case size. If you run that purifier with an E12 filter, the fraction of particles that will remain after one minute is .1 × (1-.995) + .9 = 0.9005. That’s beca…

The idea that the difference between 0.9005 and 0.90005 is "small" is … weird. The moment I read that I checked out on the rest of the authors opinions.

This is how it works because the room is not sealed, nor is the filter being used to filter outside air into a positive pressure area.

It is (hopefully) easy to see that e.g. a filter that removes 99.5% of particles, but moves twice as much air per minute will remove almost twice as many particles per minute as a filter that removes 99.95% of particles.

Using the numbers from TFA (20% of the room for the 99.5 rather than 10%):

  .2 × (1-.995) + .8 = 0.801
vs

  .1 × (1-.9995) + .9 = 0.90005
Thus proving the point in TFA that the airflow matters more than E12 vs H13. The fact that the steady state (given that "dirty" air is being introduced somehow) is lower for the filter that moves more air follows from the fact that it removes particles at a faster rate.

Re: Contra Wirecutter on the IKEA air purifier

#692

Post by thr0wawayf00 »

hoseja wrote: post #583
thr0wawayf00 wrote: post #524

Earlier quoted context omitted.

The big problem with most YouTube review channels is that they're reliant on the vendors to provide them with free test units and other forms of access in order to grow their channels, and Linus is no exception. I actually came across a "why I'm shutting down my channel" video a while back in which the host showed emails from the company whose product she was reviewing (it was a drawing tablet or something like that)…

LTT is certainly NOT dependent on free review units any more.

Maybe not, but those channels still largely rely on regular access from these companies, which always presents a conflict of interest.

I'm sure Linus does just fine in this regard, but the underlying problem still stands: if my Youtube channel's success is dependent on getting that kind of access to products early (as most top-tier reviewers do), I'm always going to have to decide between being as objective as possible and not biting the hand that feeds me.

If you've watched a handful of review videos on YT at this point, there's a pretty good chance at least one of them was pre-approved by the vendor of the product being reviewed and you just don't know it.

Re: Contra Wirecutter on the IKEA air purifier

#693

Post by jefftk »

etchalon wrote: post #682
amluto wrote: post #673

Earlier quoted context omitted.

Multiplying .9005 and .90005 by 10000 does not actually cause a 10x difference to appear. No, really, try it! If your goal is to play with numbers, you could raise them both to a large power. You would discover that the ratio between them increases exponentially, but this would pale in comparison to the fact that both results would exponentially approach zero much faster than the ratio would increase.

10000 x .9005 is 9,005. 10000 x .90005 is 9,000.5. Meaning that the first filter left 5 particles vs the second filter leaving .5 particles. A 10x difference. The goal isn't to "play with numbers" but to understand why/if the relative effectiveness of a filter results in a substantive difference in air quality. The data shows it does.

> The data shows it does

As I described above [1] the data show that the difference between 70% and 99.95% matters, not that the difference between 99.5% and 99.95% does. (And that's ignoring difference in flow rates, which is also very large.)

[1] https://news.ycombinator.com/item?id=31823047

Re: Contra Wirecutter on the IKEA air purifier

#694

Post by Darrengineer »

fooqux wrote: post #339
birdman3131 wrote: post #277

Earlier quoted context omitted.

I like a lot of project farm's videos but his electrical tape video was far off the mark of what actually matters. They were good tests for tape but bad tests for Electrical tape.

Fair, and I'd also say that many of the tests he does could really use more data points. For example, testing torque using bolts- I've had a few bad bolts in my life that were weaker than they should have been. I really hope he does that but edits it out. However, I would say that's the price you pay for an independent reviewer these days. He's (presumably) not simply reading a carefully prepared script by the vendor…

It depends on what it's being used for. Adhesion across the expected temperature range is likely the most relevant factor to consumers. The NFPA would likely not call it out specifically, and rather rely on NRTL approval for acceptability. For reference electrical equipment for use in ordinary locations (ANSI 61010), insulating tapes list UL standard 510, CSA no. 197, and IEC 60454.

Re: Contra Wirecutter on the IKEA air purifier

#695

Post by rcoveson »

etchalon wrote: post #659
rcoveson wrote: post #585

Earlier quoted context omitted.

You started this subthread with the comment: > The idea that the difference between 0.9005 and 0.90005 is "small" is … weird. When you use the author's numbers, 0.9005 and 0.90005, the implication is that you're taking the parameters of they hypothetical as given. You then go on to say that the difference between those numbers is significant. Remember that in this abstract, idealized scenario, the air filters are onl…

I started the subthread with the comment because saying the difference between those numbers is small is weird, … because it is. Those numbers represent percentages (90.005% and 90.0005%) and those two inputs, especially when applied to a chaotic system, will produce outsized differences over time. And the data shows that the two filters produced outsized differences over time. I'm not broadening the scope of my cont…

The data have nothing to do with the hypothetical where the air filters process 10% of the air in the room. They also have nothing to do with the air filters in the thought experiment, which are simplified, ideal filters that have the exact characteristics we say they do. Nobody is applying the numbers in question to any "chaotic system", because this is just a simple framing designed to illustrate exactly one, utterly banal point: If you don't process most of the air, it doesn't matter how efficient you are. In fact, that's all the section should have been. That one sentence. No numbers (it doesn't need them), and very little detail. Just, "if you don't process most of the air, the efficiency doesn't matter". You can't disagree with that conditional statment. You can argue that the premise is flawed, or irrelevant, or unrealistic to the point of uselessness, but you can't argue with the totally boringly obvious statement that if you aren't processing 90% of the air at all, then your efficiency doesn't matter. It's not more controversial than saying that "if your air filters are turned off, their efficiency doesn't matter."

Re: Contra Wirecutter on the IKEA air purifier

#696

Post by etchalon »

amluto wrote: post #688
etchalon wrote: post #682

Earlier quoted context omitted.

10000 x .9005 is 9,005. 10000 x .90005 is 9,000.5. Meaning that the first filter left 5 particles vs the second filter leaving .5 particles. A 10x difference. The goal isn't to "play with numbers" but to understand why/if the relative effectiveness of a filter results in a substantive difference in air quality. The data shows it does.

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?

Re: Contra Wirecutter on the IKEA air purifier

#697

Post by etchalon »

jefftk wrote: post #693
etchalon wrote: post #682

Earlier quoted context omitted.

10000 x .9005 is 9,005. 10000 x .90005 is 9,000.5. Meaning that the first filter left 5 particles vs the second filter leaving .5 particles. A 10x difference. The goal isn't to "play with numbers" but to understand why/if the relative effectiveness of a filter results in a substantive difference in air quality. The data shows it does.

> The data shows it does As I described above [1] the data show that the difference between 70% and 99.95% matters, not that the difference between 99.5% and 99.95% does. (And that's ignoring difference in flow rates, which is also very large.) [1] https://news.ycombinator.com/item?id=31823047

The 70% and 99.95% difference is because of the 10x filtration efficiency difference, combined with the CADR difference.

This is very straight-forward.

Re: Contra Wirecutter on the IKEA air purifier

#698

Post by IshKebab »

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.

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.

Re: Contra Wirecutter on the IKEA air purifier

#699

Post by nopcode »

SmellTheGlove wrote: post #230
bayindirh wrote: post #198

Earlier quoted context omitted.

There is also Rtings ( https://www.rtings.com ).

I wish rtings had a Boolean on tvs so we could search explicitly for non smart models. That is basically the only thing else I’d want from that site, it’s really good.

Not sure why you would care so much but this is pretty close:

https://www.rtings.com/tv/tests/ads-in-smart-tv

Re: Contra Wirecutter on the IKEA air purifier

#700

Post by jefftk »

etchalon wrote: post #697
jefftk wrote: post #693

Earlier quoted context omitted.

> The data shows it does As I described above [1] the data show that the difference between 70% and 99.95% matters, not that the difference between 99.5% and 99.95% does. (And that's ignoring difference in flow rates, which is also very large.) [1] https://news.ycombinator.com/item?id=31823047

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)

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