Talking to someone today who had bought an Ionizer. Within a few
weeks of using it, the matt magnolia emulsion on the nearby walls has
gone a dirty grey/blackish colour. Nearer the ioniser the worse it
was.
New one on me, anyone heard of this effect before?

Yup. Ended up having to redocorate the room as a result. The really, really
fine dust gets into the texture of the paint and won't wash off without
putting a seriously odd looking 'shine' on the paint.

Ioniser was binned. Never again.

Al.