Air purifiers for HDB flats, condos and landed homes

The situation most homes are actually in

Someone usually starts looking for a home air purifier after one specific trigger: haze season, a new baby, a renovation that's left a lingering smell, or simply noticing the living room feels stuffier than it should with the aircon running. What they usually don't have is a floor plan with numbers on it, which is the actual starting point. A home is not one volume of air — it's several rooms with different ceiling heights, different door habits and different aircon zones — so the right first question is which room, not which brand.

Working the numbers room by room

The formula is the same everywhere in the flat: required CADR in m³/h equals floor area (m²) × ceiling height (m) × target air changes per hour. US CDC guidance for occupied spaces is at least 5 clean-air changes per hour. Take a typical 12 m² HDB bedroom with a 2.6 m ceiling: 12 × 2.6 × 5 gives a required CADR of about 156 m³/h. That's comfortably within reach of a Fillo Plus (rated up to 30 m², CADR 300 m³/h, under 53 dB) running on a lower setting, or a Reno 500S if the room sits at the larger end of that range. The HDB bedroom sizing guide walks through this calculation with the rounding decisions that matter — whether to size to the room's actual footprint or the slightly larger figure including a bay window or yard.

Now take a 30 m² open-plan condo living-dining area, which should be sized as one combined space rather than two: 30 × 2.6 × 5 comes to roughly 390 m³/h, which sits above what a Fillo Plus can deliver and points instead to a Classic 400S (31–54 m², CADR 480, 7-layer stack). The condo living-dining sizing guide covers where a partial divider or open kitchen changes that combined-space assumption. A landed home floor works the same way but usually with a higher ceiling — a 50 m² ground floor at 2.8 m comes to about 700 m³/h, which a Pro 800S (56–96 m², CADR 800, dual intake) covers with headroom, though the landed home guide makes the case for sizing each floor separately rather than buying one large unit and hoping it reaches upstairs.

Why a closed door defeats an otherwise correct calculation

The CADR maths above assumes the purifier's air actually reaches the air you're trying to clean, and a closed bedroom door stops that mixing almost completely. A single large unit in the living room, however well sized for the whole flat's combined floor area, will do very little for a bedroom with its door shut overnight — which is exactly when most people want cleaner air. This is the most common sizing mistake in a home rather than a clinic: buying one unit for the total square footage on the floor plan, rather than one unit per room that's actually occupied with its door closed. It's also why the answer for a whole 5-room HDB flat is usually two or three smaller units placed by room, not one oversized unit in the corridor.

Choosing equipment for the room, not the flat type

A common assumption is that a condo needs a different tier of equipment to an HDB flat of the same size. It doesn't — the HDB versus condo sizing guide is explicit that the same CADR formula applies to both, and that ceiling height and floor area, not tenure type, are what change the answer. Budget is a separate and legitimate constraint, and the budget-conscious HDB guide sets out how to match coverage to a 3-room or 4-room flat without buying more capacity than the rooms need. For a landed home, the bigger cost driver isn't the address or the finishes — it's floor count and total area, which the whole-house cost factors guide breaks down before a survey gives an exact figure.

Placement and timing matter as much as the unit itself. A newly renovated open-kitchen layout carries a known filtration trade-off that's worth planning before furniture arrives, covered in the open-kitchen filtration planning guide, and anyone wanting a unit in place quickly should read the same-day delivery guide for what's realistic to promise and what actually gets a unit installed fastest. Tenants have a slightly different starting point again — purification is usually the tenant's own arrangement rather than something built into the unit, and the tenant rental arrangement guide covers what to check on move-in.

What a home survey adds beyond a self-measured floor plan

A tape measure and the formula above get most homes to a workable answer, but a proper survey checks things a floor plan alone doesn't show — door seals, aircon return paths, and where furniture will actually sit relative to the unit's intake. The room-by-room survey checklist sets out exactly what gets checked on a visit and what you walk away with afterwards, which is a more reliable figure than any online calculator on its own for a multi-room home.

What we will not claim

We will not say a correctly sized unit will cure allergies, prevent illness or otherwise change anyone's health outcomes — filtered air reduces airborne particle load in the room it's running in, and that's the honest limit of what it does. We won't describe any home as "sterile" or the air inside it as "safe" in an absolute sense, and every arrangement here, including the one-month rental pilot period, is priced rather than offered as a trial. How we word test results and certifications is set out fully on how we verify our claims.

Getting an exact figure for your home

For a single room, the size calculator gives a fast estimate using the formula above. For a flat with several rooms, a landed home across multiple floors, or a household that's outgrown guesswork, a Clinic Air Report covers a site visit at S$150 for a minimum of two rooms — every room is measured on site, with a report emailed back within two working days and a sized-right guarantee: if a specified unit doesn't reach the report's air-change figure, we upgrade or add a unit at no extra cost. From there, purchase or serviced rental — filters, parts, preventive visits and two-way delivery included — is quoted against the actual numbers for your home, not a generic flat-type assumption. Reach out via our contact page to arrange a visit.