The efficacy of the ionic things is questionable, especially in such an
open environment as a car. But if you need to get some odor out or
something like that, use an ozone generator with the windows shut. You
can buy those on EBay too. Just don't leave it on for too long if you
get a powerful one, because it could bleach fabrics. As for putting
numbers to "powerful" or "long", I have no idea. On EBay, every listing
claims it is the most powerful one by the one true measure.