Basics

A term used in Vacuum Cleaners and to a lesser extent Air Purifiers to describe a system that uses HEPA Filtration ‘’’and’’’ has sufficient Gaskets / Seals that there is no “blowby” of the filter

Main Concerns in Vacuum Cleaners

Depending on if a Pre-Motor Filter (Vacuum Cleaners) is used, anything that makes it past Filtration will make it’s way to the motor and proceed to mess that up
- A system with good filtration + a (user-replacable) Pre-Motor Filter is practically indestructible short of Motor Brushes (if applicable, re BLDC and ULTRA LONG TERM Bearings and such (especially if cheaper Plain Bearings are used
Air quality is also a concern, but some don’t view this as critical as others (hence the plethora of Non-Sealed System HEPA Vacuums being sold)

This depends on how CRUCUAL the HEPA Air Purifier is
- From a scale of “Preventing Little Timmy from getting Mild Seasonal Allergies/Reducing Dust on Surfaces” to “Top Level Biosafety Lab handling the whole mix of Plauges” the level of “critical” varies
Still though, having all the air have to go through your filter is best, and as with Vacuum Cleaners probably prolongs component life (although due to the more dilute nature of dust/debris (depending on context; in a house vs in a woodshop etc) probably makes this less critical of a point

While they rarely have a filter of such magnitude, Bathroom Exhaust Fans have similar issues with dust buildup (especially if a shower is also contained in the bathroom, as this turns it into a crude Wet Scrubber of sorts with all the Humidity)
If properly maintained, and a unit with a proper Ball Bearing etc is used, rather than sheet metal plain bearings, this is less of an issue, HOWEVER Exhaust Duct Fires can happen if old/clogged units are left running and ignored
- Albeit not as often as Dryer Vent Fires
Having sealed system hepa filtration on other equipment may make maintenance easier as well
- For instance ERV / HRVs, Computers/Servers, Various Air Cooled Pumps and such etc