Comments from you wise people?

[CalvinHobbes]

https://www.energyvanguard.com/blog/path-low-pressure-drop-across-high-merv-filter/

[JohnMo]

Looks just the same as a car air filter and the filters in my MVHR.

 

Pleating makes the filter area larger for a given foot print, not sure what's new in the article?  Having a larger surface area allows a finer filter to be installed with a similar pressure drop to a lower performance flat filter.

[CalvinHobbes]

Cheers

 

[SteamyTea]

Air filtration is not always about the pore size.

High performance car filters have a very course mesh. This slows the airspeed (actually an acceleration in the negative direction), allowing fine particles to drop out of suspension.

Very high performance air craft filters do the same but enhance it with centrifugal forces.

Edited March 28, 2022 by SteamyTea

[markocosic]

They're cheap in standard sizes compared with mvhr unit filters too

[dpmiller]

filters can be a ripoff. The media is cheap- look at the average car spraybooth, the non-woven media used is about £2/ m2. But cut it into a wee piece for (say) a fume hood or even an MVHR and well...

[markc]

A lot of HVAC and dust extraction systems are poorly designed (if at all) and installed.

filters can be too small or too large, air flows can be too low or too high. 
no use having a very fine filter with high air velocity as the small particles behave like bullets or shot blast material and destroy the filter as they hit it.

[SteamyTea]

Used to make air filters.

The smaller the better as they cost pennies to make and it made the technology seem better.