Only Sharp – three models – and one by Whirlpool, in the Fortress store I tried (Central). Got a Sharp FU-P60S – after first having a look in the store, then heading home and doing a bit of reading around on Internet. Reviews for this and/or related models looked good, with a few people reporting decreases in allergies etc (in US; maybe from some household stuff like dust mites?).
Info on Sharp site: FU-P60S – says it’s 99.97% efficient vs particles of 0.3 microns, which may mean fair numbers of even tinier particles get through. Cost HK$2500, using HSBC card (bit of discount): so I hope it works! (Does tend to have orange lamp – for dirty air – on as start operating; but goes to green, for clean, after a few minutes.) Heard of a purifier costing HK$9600 (ouch!) in Bumps to Babes, down from over HK$12,000. For dough like that, gotta hope it also does the vacuuming and ironing…