> the HEPA filter works by having an injected electrostatic charge which will leak away over time
Nope, HEPA filters are not dependent on electrostatic effects and do not magically start leaking. When they are too loaded with dust, air has a harder time getting through, which is the main factor that causes them to need replacement.
I can't edit my comment any more, but on researching, I see you are correct. I thought I had read that HEPA used electret material like FFP3 filters, but most do not.
Nope, HEPA filters are not dependent on electrostatic effects and do not magically start leaking. When they are too loaded with dust, air has a harder time getting through, which is the main factor that causes them to need replacement.