You have to look quite carefully because "HEPA" became branding rather than rating, and you can find it labelled on filter appliances which vary in capture rates by several orders of magnitude.

You want ones with numbers, 99.97% is a good number to find, you can get it on big Honeywell filters.

While incredibly difficult to find, there are MPR 2800 rated furnace filters which are better than HEPA.

Careful though. Those things can destroy your hvac system, which is not designed to deal with a severe restriction like that. Plus, they won’t last long with no pre-filtering at all. Shame to have a great filter like that just clog up with hair and pollen in three weeks.

If you're recirculating the air through the filter many times, the capture rate doesn't really matter. What you don't catch on the first pass you'll catch in the 2nd.

From that point of view, even a 90% catch rate sounds fine.

When you're dealing with a machine that is exchanging air in a room a certain number of times per hour and a continuous influx of particulates, with less efficient filters you need more air exchanges which means more filters, bigger fans, etc.

The takeaway is that less particle efficient filters won't ever get you down to the same steady state as better filters in real world applications.

And from personal experience with filters and devices to measure airborne particles, it is hard enough getting good numbers with the best filters I can find.

If I were you I’d sign up for Consumer reports and buy their second highest rated air filtration product. The most expensive one tends to be really expensive and the second best tends to be almost as good at a significant discount. This is how I make most large purchases these days.

After looking at CR and buying quite a few others I'm pretty solid on alen.com standalone units, altho a central HVAC definitely seems more effective, esp. given that you aren't necessarily recirculating a build-up of CO2 all night long.

I got a cheap tower Holmes from Walmart for not that much (less than $100) and I put 2 99.99% filtration HEPA filters in it and have been running at half speed most of the day for over a year.

I shake out the pre-filter (gets covered in dust and pet dander) and toss out the filters every ~6 months. I use a filtrate 1900 filter for the home air filter.

Tip: never use the "ionic" button. They come on most filters for some bizarre reason, but ionically charging the air is a bad idea.

“ ionically charging the air is a bad idea.”

Why?

Ionic means ozone generation. The idea with charged filtration is that microbic particles are attracted to the filter. However, ozone is a lung irritant.

> Ionic means ozone

No it doesn’t. Who told you that? Ozone generators are a completely different thing and air ionizers must conform to low ozone emission standards.

> > Ionic means ozone

> No it doesn’t.

Yes, it does.

> Who told you that?

Among others, the EPA [0].

> Ozone generators are a completely different thing

They are, but ionizing air cleaners still generate ozone even though they are different than “ozone generators”. [0, again]

> and air ionizers must conform to low ozone emission standards.

No, only the small minority that claim health benefits in a manner which brings them under FDA medical device regulatory authority do. [0, again.] But even those so regulated in ozone emissions are net ozone generators.

[0] https://www.epa.gov/indoor-air-quality-iaq/what-are-ionizers...

Getting a filter that is properly sized for your space and that meets your unique requirements (ACH, efficiency, etc) is likely sufficient.

Here’s an outline on how to go from the common rating, CADR, to various parameters that are of interest:

https://frdmtoplay.com/nagivating-air-purification/

In terms of bang for buck nothing comes remotely close to having a furnace filter strapped to a 20" box fan. This gets you most of the benefits of an expensive filter for a fraction of the price.

People will talk about CADR but also look at TCO.

It’s only a good price for a bit though. Without any kind of pre-filter, large dust will clog that expensive near-hepa filter in a couple months. Plus, an axial fan can’t really move air though a good filter very well.

I still recommend just spending the 150 bucks on a Winex or Coway. Then you have true hepa, plus filters that last a year.

*Winix

Dyson