Simple, just check the filter if you don't trust such products.
If the filter is very dirty over some time of usage, then it's doing it's job.
It works like an aircon, so we must be aware that our living environment is dusty & make some improvements.

Ionizer is a tricky business. There are lots of useless product in the market such as USB Ionizer or cigarette lighter plug-in Ionizer, which cost less then RM50.00

So far the best Ionizer in M'sia market is Medklinn
It's for out & indoor use.




I placed my nose near the Medklinn Ionizer, i can really smell the negative ions. Impressive!
But it comes in a hefty price of RM300 for the car Ionizer.
Can't imagine how much will it cost for the indoor model....