[himata4113]

You don't really want to use HEPA either, you want to maximize airflow.

PC fans with low MERV type filter do great since the smaller the particle (I think this effect kicks in below 5 microns) the better it is at filtering it so if it can pass 10 times more air than a hepa filter it's as effective as one while being able to filter more air faster and keeping the particles airbone.

The only downside is that small range of particles where lower merv filters aren't good enough to filter so upwards of 70% of the particles pass through

[schiffern]

Agreed. MERV 11-14 can be far more effective than HEPA.

If you need to filter "one and done" (like pumping air into a hospital operating room), that's where you need HEPA. Most home air purifiers mix the clean air back into the same room, so MERV is closer to the ideal sweet spot.

It's also important to buy reputable brands of MERV filter, ideally ones which have a large number of folds (surface area) like the 3M 1900 MPR. In recent testing about half of filter brands scored well below their claimed MERV rating:

https://www.youtube.com/watch?v=FKAVek1YaSQ

[ajb]

That sounds worth knowing; however when I looked MERV up, it seems that it's a rating system, not a type of filter. Could you be more specific abot the kind of filter you mean?

[himata4113]

HEPA is typically just one type of filter with True HEPA as an offspring, MERV is a range which allows you to filter exactly what you need at the highest airflow. It really depends on what kind of pollution you have at your home.

If you just have a lot of dust then you want highest airflow possible (around MERV 9-10) if you want to filter things that cause allergies you need to go as high as MERV 14 since MERV 9-10 effectiveness is super low in that specific range.