What to Know Before Buying an Air Purifier to Clear Wildfire Smoke | Hacker News Reader

What to Know Before Buying an Air Purifier to Clear Wildfire Smoke

nytimes.com

53 pointsSREinSF33 comments

The air purifier market is riddled with false marketing claims bordering with fraud. I wanted to buy a purifier once but after doing some research I become so disillusioned that I abandoned the idea. Some of the problems I found:

* If the filter is not true HEPA it is probably a garbage. Beware any HPP or HEPA-like nonsense.

* If the filter is no-maintenance it is not filtering anything.

* Check the price of the replacement filters first, it is the same business model as with printer cartridges.

* The square feet or square meter characteristic is meaningless/arbitrary, you need to know the air volume per time.

* Whatever "Allergy Association" certificates are probably meaningless marketing.

* Pre-filter makes sense - it prevents hair and bugs from clogging the HEPA filter. Any other type of filter is probably garbage, there is usually no data or metrics for efficiency.

* The typical carbon filter is probably totally useless, you would need a solid quantity of carbon to absorb anything, not just carbon film or fibres.

* The efficiency of the UV lamp for killing viruses and bacteria is questionable, at best. The germicidal effect is a function of the correct wavelength, dose and exposure time. No data as usual.

* The ionised air and ozone may be bad for you and there is no data or metrics on how much ions/ozone you get.

To add insult to injury most of the purifiers look as if they were designed in the 80's and will blemish every room.

I will invoke the Gell-Mann Amnesia effect - if a company misleads you with a film-like carbon filter, what is the chance they are telling the truth about the HEPA filter, the flow rate or the noise level?

A polycyclic aromatic hydrocarbon called retene — emitted from forest fires — causes severe DNA damage. I don't think HEPA filters, like the ones described in this article, remove PAHs in general.

"Pollutant emitted by forest fire causes DNA damage and lung cell death"

https://www.sciencedaily.com/releases/2017/10/171024115604.h...

A lot of air purifiers come with activates carbon pre-filters that should take care of most volatile organic compounds. I'm not sure how effective they are in practice but this paper suggests that activated carbon is used in aqueous solutions to remove PAH; https://www.ncbi.nlm.nih.gov/pubmed/26820781

So you're probably better off than not buying one of these things

From the article:

"In order to be effective, the activated charcoal filter would have to be a minimum of five pounds to have any statistically significant effect, he said."

I've never seen such a device.

https://www.amazon.com/gp/product/B00D7M6692/

These types of filters get as big as you could possibly want

Water gets surprisingly less coverage as a particulate trap than woven filter media, but it can work better for most use cases, afaiu. Air washers and indoor water features clean air by electrical attraction on contact and then lose some water to evaporation, so you may also need a dehumidifier. They have a higher, more consistent particulate reduction than HEPA, and no lower bound particle size limit, and they don't lose efficiency from filters clogging through use. You can also add a small UV-C light as an antimicrobial, and they are very simple to build.

Earlier this summer I researched air purifiers because of a large painting project that was going to take place in my residence. I am super-sensitive to smells and the like, and I was not going to mess around with this purchase. I ended up choosing the EnviroKlenz mobile air unit.

There are no two ways about it: the unit is expensive. However, it does not resort to using carbon, which can end up releasing pollutants, and I was told the product gets used in clean up operations by the government.

I would not call the purchase a perfect panacea, but I believe it helped, and do not regret it.

https://enviroklenz.com/remove-toxic-paint-fumes-fast/

https://enviroklenz.com/large-wildfires-in-washington-oregon...

The SweetHome (part of the NYT Company!) did not review EnviroKlenz, and I believe that is because of the whole Amazon affiliate aspect to the SweetHome.

(I'd be curious if others here have used EnviroKlenz.)

it does not resort to using carbon, which can end up releasing pollutants

Sounds like misinterpreted marketing FUD.

Also, correct me if I'm wrong but fundamentally HEPA is about removing tiny particles whereas other approaches catch larger particles, and organic fires mostly release larger particles. HEPA filters for your house are extreme overkill, it's like living in a medical lab.

I am in no way, shape, manner or form affiliated with EnviroKlenz! That out of the way, here's a blurb from their article:

"Activated carbon filters will remove chemical gasses. They work by adsorption, a process by which the toxic gasses are attracted to and stick to the carbon But there are problems with carbon filters. Since activated carbon simply collects toxic gasses and stores them, when the carbon becomes full of gasses, the gasses can release back into the air."

That is what I was referring to in terms of carbon not being a cure-all.

Marketing FUD - nothing is a cure-all! No filter lasts forever! If you don't maintain a filtration system it will always fail! Common failure modes are reduced throughput and reduced efficacy. Carbon is cheap and effective for many requirements, which is why it is so commonly deployed.

So would a box fan + furnace filter in the window work for the large smoke particles? DIY wood worker people make rigs like for dust in their garages.

I've done that and it does work as a filter in general.

The first thing to note is that furnace filters are not HEPA filters. The second thing to note is that HEPA filters don't filter out the same things as activated charcoal (from what I understand).

Box fans don't work especially well with the backpressure. You'll get vastly less air flow. I think the dust-catching products I've seen like http://www.leevalley.com/us/Wood/page.aspx?p=65482&cat=1,424... are a lot less restrictive than a couple furnace filters across the front of the fan.

Plants might be a cheaper option

https://en.wikipedia.org/wiki/NASA_Clean_Air_Study

That's for long term air quality though. The speed at which they remove pollutants is much lower than a filter.

What pollutants does activated carbon release?

Thanks for the information. About how often do you have to replace the filter in that unit?

My son has some lung problems and is sensitive to dust and smoke. I recently decided to get HEPA filters for the 3 bedrooms and replace the decade+ old Holmes unit that was starting to look worse for the wear and I had been using in the kitchen while I was remodeling.

I ended up going with the Coway unit the Wirecutter recommends and have been pretty happy with it. One nice feature that seems to work pretty well is that it has a particulate sensor and an "auto" mode that adjusts the speed based on particulates in the air. The normal mode is super quiet, but when it detects gunk (often triggered by walking into the room), it will kick up the fan for a bit.

I don't always love the Wirecutter/Sweethome choices, but in this case it directed me to a product I wasn't even considering and I was happy with it.

Always read the details of the reviews, what they find important may not match what you do.

and they will cycle the air four to five times per hour in a room that size,

Is that all the air or part of it? And does that matter? i.e. anyone knows whether smoke particles etc automatically dillute or rather stay in the same concentration given one volume of air? I mean, I can imagine if you put one of these things in the center of the room, it will take in air and spit it out, but unless there is some constant process also taking volumes of air away from the far away corners, behind tables/beds/couches and getting it to be sucked up by the machine, the machine is always cleaning the 'same' air hereby leaving volumes of air far away from it untouched and hence possibly still polluted? Or isn't that how it works because there always is some kind of air flow going on somehow leading to all air making it through the machine?

Most rooms do have dead spaces where the "age of air" is higher than the well-mixed parts of the room. So you can expect some of the room air to go through the filter more, and some less.

There are a few reasons this effect probably doesn't matter so much. First, the dead spaces tend to be places where people don't breath -- in closets, under furniture, in corners, near ceilings, etc. Second, where people do go, they bring thermal plumes and activity-generated eddies, which tend to mix up room air. In fact, the act of breathing also provides mechanical power that will promote mixing. The filter itself also blows air, giving more mixing than if the filter wasn't present.

The net effect is that the participating volumes of the room, where people tend to breath, probably get mixed at a rate similar to, or greater than, the rate at which the filter scrubs the air. Any non-participating volumes act as slow-filling and slow-releasing reservoirs, which delay the room's response to changes in outdoor concentrations.

I would worry more about the filter only cycling the air 4-5 times per hour. That's probably faster than the effective release rate of the indoor sources with which Mr. Hefferman (the expert cited in the NYTimes article) seems to have have experimented. However, it's the same order of magnitude at which outside air gets into most houses (especially in the parts of California affected by these fires). My gut feeling is that implies the filter isn't going to keep up so well -- though I'd want to model it to say anything definitive.

FWIW I believe it helps to run ordinary fans in the room in tandem with a filtration unit to combat the airflow issues.

Thanks, that was a nice explanation.

Except the part where I spelled "breathe" incorrectly :-)

From personal experience I run a high quality filter in my bedroom. In september we had serious (just straight up hazardous) air quality issues and you couldn't even appreciably detect smoke in my room or the nearby rooms. Walking outdoors felt like wandering into a cigar bar.

Personal recommendations for the IQAir brand, and hearsay discussion that Austin Air also makes good products. Costs about $120-$180 a year, worth every penny.

Once had a huge screw in a brand new Austin Air that I purchased. As soon as it was first turned on, it produced a large banging sound where upon inspection, the rotors of the intake fan had violently been broken off, and a 3 inch screw lay. Austin Air refused to assist with repair or replacement and instructed me to contact Walmart instead. Austin Air used to be my goto brand but their quality has eroded. Many of the newer units have bent metal joints and other abberations but are still sold. Go with another brand, Austin Air does not deserve our business.

IQAir is great. But if on a budget, I can recommend Coway. They are really efficient, use little energy and not expensive at all:

http://thesweethome.com/reviews/best-air-purifier/

I personally own a 1008-DH, which has much better filtration than the 1512 reviewed there.

Previous reviews at The Sweet Home also analyzed IQAir, which is probably even better as it filters particles down to ~0.1 microns. I'd love to see an unbiased review testing ultra-small particles.

I had an IQAir for years. It was expensive, the filters were expensive, and it rattled a lot on certain settings because of the way the motor resonated.

Strange. We have 5 IQAir HealthPro 250 machines in our apartment, and none of them have ever emitted a rattling sound, even though we use most of the settings (going all the way up to 6 only on the most polluted days).

EDIT: Yes, the filters are expensive. We've started using aftermarket ones, which look cosmetically a bit different but seem to have the same core materials. Still expensive, but I like the machines due to the airflow/noise ratio. Cheaper ones I've tried are all to noisy if you put them on a high enough speed to be useful.

In my experience, using them for pollen, buy the largest ones and you can run it at the lowest level so that it's quiet and the filter lasts the longest.

I've had the Kenmore-branded version of the Whirlpool Whispure AP51030K. I see some suggestion that the newer ones since they sent production overseas are a bit lesser quality, but the price is certainly less than I paid a decade+ ago. Nice feature is that there is a separate replaceable pre-filter for dust.

3M used to make some, but discontinued them. I have a couple of those.

Honeywell also makes some decent ones, though I haven't used them personally.

Unfortunately I've not seen anyone making a HEPA filter that uses standard-sized furnace filters, which is unfortunate because the better versions of furnace filters (e.g. 3M filtrete "purple") are about equivalent to HEPA filters and usually cheaper. The discontinued 3M air purifiers used a different size, I suspect to keep up a razor-blade business model :/

On the other hand, if you have forced air heat/ac (I do not) and if you use the better furnace filters you might be fine just running that (including a fan-only mode if possible).

Why are Air Purifiers so expensive? Does there need to be something inside them except a prefilter, a HEPA filter and a fan?

Not on the list but have owned two vornado hepa filters over the years and they work extremely well

I think there's perhaps a good argument all inner-city houses should have these.

Perhaps all homes?

We know small particles kill. It's why smoking kills not nicotine afaik.

I get the cubic law, so comparing smoking to dust and long distance smoke is not quite the same. But I'd like to see the proper figures.

These devices extend our lives for how long? in what locations?

Wow, nice ad, also what an epic deception.

These filters are designed for everyday use.

Cleaning smoke polluted air should be considered extreme use.

Even if you are getting an industrial filtration system installed,

you'd had to change filters almost daily.

It's the same if you get a kids pool filter for a large pool, it's useless after a day or two.

I really hope these people will get proper help to restart their life, these protip articles are super concerning.

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