Most air purifier listings are written to make you feel something. This guide is written to make you check something. If you only have time for one rule, it is this: buy for airflow in your room and a real filter, and ignore everything else until those two are sorted.
The checklist below works whether you are shopping on AliExpress, in a mall or on a brand site. We have not tested the products we link to, so treat our picks as a shortlist and verify the details on each product page.
- Start with CADR, not coverage
- Check the filter grade
- Noise decides whether you keep using it
- Price the filter before the machine
- Extras that help and extras that are noise
- Pick the room, then the product
- FAQ
Start with CADR, not coverage
CADR (clean air delivery rate) tells you how much filtered air a purifier delivers, usually in m³/h. Coverage claims in square metres depend on assumptions the seller does not show you, so turn them into airflow instead.
Rule of thumb: room volume (length x width x ceiling height) multiplied by 4 to 5 air changes an hour gives the CADR you want. The CADR calculator does it in seconds, and the room size guide shows worked examples.
Check the filter grade
Haze is dominated by fine particles, the size range HEPA filters are built to capture. Look for a stated grade such as H11 to H14, or a test standard on the product page. "HEPA-type" and "HEPA-like" are marketing, not a grade. More in HEPA vs ionizers.
Activated carbon helps with odours and some gases, such as the smell of smoke. It is a useful extra, not a substitute for the particle filter.
Noise decides whether you keep using it
A purifier you switch off because it is too loud has an airflow of zero. Check the dB figure at the lowest speed, since that is where a bedroom unit will live, and read recent buyer comments for the honest version.
Price the filter before the machine
Filters wear out, and a haze season can wear them out faster. Before you buy, check the replacement filter price, whether it is sold separately, and how often the seller recommends changing it. A cheap purifier with an unobtainable filter is a countertop ornament with a plug.
Extras that help and extras that are noise
A display and a PM2.5 sensor are handy. App control is nice if you will use it. "Sterilises 99.9%", "negative ions" and "medical grade" are sales copy until the listing shows evidence. Ignore them and go back to CADR and the filter.
Pick the room, then the product
Browse by room: bedroom and small rooms, living rooms and big spaces, car and desk. Or check what is hot in Singapore right now.
Quick answers
Do I need a HEPA filter for haze?
Haze is mostly fine particles (PM2.5), the range HEPA filters are designed to capture, so a real HEPA filter is the sensible baseline.
Is a bigger purifier always better?
Not always. A unit far larger than your room costs more, takes more space and may be louder. Match CADR to your room volume, and size up only if doors are often open.
How often should I change the filter?
It depends on the model and how much you run it. Follow the seller's guidance, and expect to change filters sooner after a heavy haze season.
