This article definitely supports it, however has anyone actually ever felt that much difference after getting their purifier?
If it makes a difference and you want something that sounds different or has some extra features, then you could get a nicer one.
It’s hugely noticeable with smoke, for instance. Humans don’t have a great sense of smell, but we do very well with smoke. The difference between air with <1% leftover smoke and air with 13% leftover smoke is obvious to everyone.
The EPA has a lot to say about this, if you’ve the patience to wade through it — https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-...
You shouldn't end up with 13% leftover, if you're doing it right. Air will pass through the filter multiple times, and it removes >75% each time.
Below MERV14, you'll have that problem. Above, it should do as well as HEPA. The gap between 13% and 0% will be made up for with a 13% stronger fan.
A filter with 99% efficacy at a flow rate of 30cfm will remove the same amount of stuff as a filter with 50% efficacy at 60cfm.
A 99% sealed HEPA system isn't cleaning the air that's not passing through it right now, which is most of the air in the room. It reduces the pollution by some nominal rate. After it's been running for a while, the air is a lot cleaner.
The major problem with box fan with filter are noise, aesthetics, and similar. Box fans aren't designed for for high loads, and just don't work great in that context. It will clean the air just fine, but a proper filter will do so much more efficiently and pleasantly.
In terms of effect:
I have allergies. I feel a lot better post-COVID, with HEPA filters, face masks, and similar precautions everywhere. I can't pin that down to any root cause, though. Particulate pollution? Allergens? HEPA filters at home? Masking outside. Dunno.
I think fan blades aren't that efficient at pushing against the high flow resistance of a HEPA filter, while the squirrel cage blower in a dedicated air purifier is.
The answer is easy: A self build system blows the air through a filter. Nearly all commercial systems suck the air trough a filter. Big difference.
I can believe that some home built box fan purifiers out perform some commercial units, but not as a blanket statement that a home made filter outperforms all commercial units.
> A self build system blows the air through a filter. Nearly all commercial systems suck the air trough a filter. Big difference.
But if you’re strapping a filter to a fan, it’s probably more efficient to blow through, since the air will be more focused (plus, it’s easier to mount due to front being flatter).
> I can believe that some home built box fan purifiers out perform some commercial units, but not as a blanket statement that a home made filter outperforms all commercial units.
Agreed. I recall seeing the stats they published and it looks like there are good purifiers among the more expensive ones (US$1000+), but apparently even in that price class they’re hit or miss and don’t always perform as well as a DIY solution could. Generally there’s a lot of information asymmetry, manufacturers want their margins so commercial air purifiers might often use something custom rather than a standard-compliant HEPA filter (either worse or slightly better but 10x more expensive than it should be) and make it difficult or impossible to swap it for something from a trusted third party. They’re counting on very small percentage of customers having properly calibrated particle counting equipment set up at home, they get away with providing misleading tech specs like CADR (or not providing them at all), and so on.
May be my air quality was already pretty good. I will check the status of the filter after a few weeks to see how much purifying it had to do.
I have a $100 HEPA air purifier, and separately an air quality monitor. I live in a very residential area of Brooklyn on a side street.
On normal days the air purifier makes absolutely no difference because PM10/PM2.5 are relatively low just generally.
But the other week when wildfires were producing smoke that smogged up NYC? It absolutely made a difference (brought indoor levels back to "normal", far lower than outdoors that day) and I was happy to be able to run it.
Before you buy a purifier, buy an air quality monitor. This is the one I got, based on reviews it seems to be the most accurate for any under $100:
The article clearly states that the best way to "clean" the air is just to bring in more fresh air from outside. The article doesn't strongly support filtration unless your outside air quality is poor.