How we rank purifiers and calculate our estimates

Every recommendation on purifierplan.com comes from the numbers and rules on this page and the choices you make in the planner. Commission plays no part, and no brand pays for placement.

Money

• Some retailer links are affiliate links (Shopee, Lazada, and Amazon where shown). If you buy through one, we may earn a commission. It doesn't change your price.
• The ranking code never reads which retailer a product is sold through, or whether we have a link for it.
• Where we have no affiliate link, the button says "Find on Shopee". It's a plain search that earns us nothing.
• If a brand ever paid for content, it would be labelled "Advertisement". None has.

Which products can be recommended

• Each product's output (CADR), power, noise, filter interval and price are recorded with the date we checked them (currently 10 October 2026).
• Tested means a smoke CADR verified under the AHAM programme. Brand's figure means the brand's own number, often under a different test method. We show which is which, everywhere.
• Models whose specifications we could only find on retail listings are shown in comparisons but never recommended until we verify them.
• Models that publish no comparable output figure are never ranked.
• You can limit picks to tested models, or to models with no ioniser or UV lamp.

How a room is sized

1. Clean air needed = room volume × your target air changes an hour (3, 5 or 7; 5 by default).
2. Medium speed: if you size for medium speed (the default), we assume a purifier delivers 70% of its rated output, so the rated output needed is divided by 0.7.
3. Open-plan spaces (living, dining, kitchen, corridor) are sized together as one body of air, with 10% extra because air mixes less evenly across them. Bedrooms with doors shut are sized on their own.
4. Up to 3 units per room for homes, 6 for business spaces.

How picks are ranked

For each room, every eligible model (and 2 or 3 units of it, if one isn't enough) gets a score. Lower is better.

Total cost is price plus filters plus electricity over the period you choose; running cost is filters plus electricity. Each cost is divided by the cheapest option for that room, and each 10 dB above the quietest option adds 1 to the noise term. "Quieter picks in bedrooms" (on by default) adds 0.35 × noise in bedrooms and other quiet rooms. Each extra unit adds 0.12, because fewer units are simpler to live with. The top score is tagged "Best match"; the cheapest and quietest alternatives are tagged too.

Budget mode

If you choose 1, 2 or 3 purifiers (and optionally a spending limit), the planner tries every combination of rooms and models within those limits. It keeps the one that removes the most haze from what people breathe at home, weighting each room by the hours spent in it. It also considers carrying one purifier between the living room (day) and a bedroom (night) and uses that when it does better.

Estimates

Noise at the speed a room needs

Noise ≈ the higher of the quietest published figure and (top-speed dB + 50 × log₁₀ of the speed fraction), plus 10 × log₁₀(number of units). It's an estimate from published figures, not a measurement.

Electricity

Power ≈ the higher of the lowest published wattage and (top wattage × speed fraction³), for the hours each room is used, at the SP Group household tariff (31.16¢/kWh with GST for October to December 2026). You can change the tariff.

Filters

Replacement filters at the manufacturer's stated interval and our recorded price. The first filter comes in the box.

Coverage map

A room's average air changes = clean air delivered ÷ room volume. Within the room, spots further from the purifier get less, falling off with distance; air reaching a room through a doorway falls off from the doorway. A purifier within 0.3 m of a wall loses 15% of its output. A "dead zone" is any spot below half your target. This is a deliberate simplification to show where coverage is thin, not an airflow simulation.

The air you'd breathe

Indoor fine particles (PM2.5) are estimated with a standard steady-state balance: indoor = P × a × outdoor ÷ (a + k + q), where a is outdoor air leaking in (0.6 an hour with windows shut), P the share of particles that get through (0.9), k particles settling (0.2 an hour) and q the purifier's air changes an hour. These values are calibrated together to match Singapore measurements during haze (indoor at 62–72% of outdoor with windows shut or air-con on); they weren't measured separately. With windows often open, a = 5 and P = 1.

Outdoor PM2.5 comes from NEA's reading for your region, or is converted from the PSI using NEA's breakpoints (how that works).

"Less haze breathed" is the drop in PM2.5 you'd breathe at home compared with no purifier, weighted by the hours spent in each room. We compare results with the WHO 24-hour guideline level of 15 µg/m³ as a reference point. These are estimates of exposure, not health outcomes.

What we don't do

• No health or disease claims, personal risk percentages or cigarette comparisons.
• No endorsements: we're not affiliated with NEA, MOH, HDB, SP Group or any brand or retailer.
• No checks of building, licensing or workplace requirements for childcare centres, schools or offices.

Corrections

Prices and specifications change. If you find an error, tell us and we'll fix it and update the date on the page.