The short answer is no, it’s not a good idea. It’s tempting. As with most imported or foreign brands in China, a new, reputable air filter is much more expensive here than if purchased abroad. However, bringing air filters from markets such as the US and Canada that run on 110V/60Hz and converting to run on 220/50Hz once in China poses a few problems:
1. Damage resulting in equipment burning out. For motorized equipment, you need to think about the cycles (Hz), not just voltage (V). A more technical explanation of the electrical effect is available here. Effectively, you run the risk of burning out your nice new air filters. I’ve heard this from my filter distributors and come across two burned out IQ Airs, which at about US$900 each (overseas prices) is a bit of a set-back.
2. Warranty coverage. If you do have problems, filter manufacturers’ warranties don’t cover electrical damage due to transformer use.
3. Additional cost of running a transformer. Air purifiers are meant to be kept on 24/7. Most air purifiers for about a living room size use about 50-100W. Transformers are always on as opposed to demand-driven. Since a transformer should be about 30% over what you need, you’ll probably be running a 150W minimum, and in China, transformers above 80W step up to 300W. So, even if you ran the purifier on the lowest setting (about 30W), you would still be burning 300W around the clock (10x). With the planned introduction of progressive residential electricity rates across China, not very cost-effective or environmentally conscious.