Non-entity wrote:
....

There were electronic filters before, they performed very poorly (they arced
more than they cleaned anything, and I'm convinced they let an awful lot of
large particles go on through, and some of the techs have told me the gaps
between the collector plates and ionizing wires were so big a lot DID get
through). This Trane unit is supposed to be better.
....

Have one of those still and can attest to the significant difference in
visible dust motes and in obvious improvement in my mother's allergies
that they are quite effective for dust and pollen allergens. Don't
know about actual measured by particle size efficiencies, but if whole
house (as other respondent notes) and run, I'm convinced they are very
effective for that purpose. Whether that's what is needed for your
mother's best improvement is another question.

--db in sw ks