There isn't one. The reason why Sharper Image went out of business is because the Ionic Breeze was proven to be ineffective product and harmful to use in some cases based on Consumer Reports data as well as data from the EPA. They sued Consumer Reports, lost the case, and had to pay all the legal bills.

The Consumer Products Safety Commission is going to making decision on all ionizers by the end of the year. It's quite possible that no one will be selling them anymore.

There is thread I left in the Ionic Breeze section about the EPA data on ionizers and the harmful effects of using them as well as a link about what happen to Sharper Image.

This product should have been regulated a long time ago. Orek and few others are going to be pulling the plug on them real soon.