The Friedrich Air Cleaner C-90B costs more than most, but in an independent test it had far better results. To see a February 2008 consumer report on this product, cut and past the following link: http://blogs.consumerreports.org/home/2008/02/air-cleaners.html
The filter removes particles as small as .01 microns compared to .5 with a media filter and only 10.0 with a standard filter. It uses a prefilter for large particles, ionizes smaller particles and attracts them to collector plates, then removes odors and fumes with a carbon filter before clean air recirculates back into the room. It clears 100% of tobacco smoke from a 10'x12' room in just 20 minutes!
You must clean the filter once a month. If you do, you will see its performance return to its original high value. You can clean the Friedrich's filter in your sink or dishwasher. This cleanable filter is less expensive to operate and more ecological since you don't have to throw filters away.
Friedrich Electronic Air Cleaner 
The Friedrich Air Cleaner C-90B costs more than most, but in an independent test it had far better results. To see a February 2008 consumer report on this product, cut and past the following link: