Air ionisers make a mess

A real air ioniser (ionizer) puts a mild electrostatic charge into the air that causes dust, pollen and other microscopic airborne contaminants to precipitate out to adjacent surfaces. The best way to test operation of one is to put a clean sheet of white paper under it. After a while the sheet of paper will have gone darker where it wasn't covered, due to dust precipitation.

The downside of a simple ioniser is that the stuff that precipitates out makes a mess in the general area of the ioniser.

The upside is that it does actually precipitate contaminants out of the air at a molecular level much finer than a filter can achieve.

There are ionisers with opposite polarity dust collection plates that act as a preferred surface for dust to stick to.

A modern ioniser is silent and uses less than a watt of power.
The classic voltage multiplier types common in Europe use about 0.1W of power.