Phil -
Ions are just atoms or molecules that have a charge -
that is, they have more or less electrons than protons. To create an
ion, you take an atom that has the same number of electrons as protons
and remove or add one or more electrons. There are quite a few ways
that this can happen - commercial ion generators are just one.
One
of the most common kinds of ion generator is a machine that simply
generates a high voltage an places this on a surface with one or more
tiny sharp points sticking out of it. The electric fields at the tips
of these sharp points will be very large, and this will in turn cause
ions to be expelled from the region around the tip.
Some of
these ions will stick onto small particles in the air - such as small
bits of dust. In fact, this is how electrostatic air clearers work - in
these devices the charged dust particles are attracted to a nearby
grounded metal plate or rod.
Some great information is available at
-Tamara & Mats
(published on 10/22/2007)