How good are HEPA filters?

[Regulo]

Just watched a TV programme about vacuum cleaners (yeah, that's how sad I am!). I was astounded at just how good HEPA filters are. I had no idea.

 

[Pink Duck]

Watch Tesla’s HEPA / Bioweapon Defence Mode demonstration video, a better example of the rapid drop in particulate count (PPM). Typically 1 minute to clean and within 5 minutes barely detectable. I keep cabin positively pressured all the time to prevent the 17% of inflow from cracks/gaps.

Also put a fresh HEPA filter in my dehumidifier last night, noticing how much better the seal was and finding just 30 PPM in condensate after, good enough for car pressure spray pot to avoid water spotting