Haze season in Singapore: sizing, rental and preparation

When the PSI starts climbing

The pattern is familiar to anyone running a clinic, preschool or office in Singapore: the sky changes colour over a weekend, the PSI readings start moving, and within days every waiting room and staff pantry needs an answer. This is not a planning exercise with months of lead time. Haze is a short, sharp event, and the buyer who calls us in week one of a bad patch usually wants three things clarified quickly — what size unit actually copes with the room, whether buying or renting makes sense for something that might last three weeks or ten, and how fast equipment can actually arrive once a decision is made.

The short answer to all three sits in the same place: sizing by room volume, using a filtration stage built for fine particulate, procured in a way that matches how long the haze episode actually runs. Our sizing guide for haze and the rental guide for haze season go through the detail; this page sets out the reasoning behind both.

Sizing is a PM2.5 problem, not a germ problem

Outside of flu season, most air purifier sizing questions in Singapore are framed around occupancy and airborne pathogens. Haze changes the framing. PM2.5 is a continuous outdoor source seeping in through doors, lift lobbies and imperfect seals, so the job is to keep a room's air turning over fast enough that particulate concentration stays down, not to chase a single contamination event.

The working formula is straightforward: required CADR in m³/h equals floor area in m² multiplied by ceiling height in m multiplied by your target air changes per hour (ACH). A 40 m² waiting room with a 2.6 m ceiling, aiming for the US CDC guidance of at least 5 clean-air changes per hour, needs a CADR of roughly 520 m³/h. Push for 6 ACH and you are closer to 624 m³/h. The relationship between ACH and clearance time is direct: clearing 99% of an airborne contaminant takes approximately 276 divided by ACH, in minutes — so 2 ACH takes about 138 minutes, 5 ACH about 55 minutes, 6 ACH about 46 minutes, and 10 ACH about 28 minutes. During haze, faster clearance is worth paying for, because outdoor PM2.5 keeps re-entering the room every time a door opens.

Under-sizing is the most common mistake we see once the PSI climbs — a unit bought for a small consultation room gets moved into a 60 m² open clinic floor because that is what's on hand, and the CADR simply isn't there to keep up. Our sizing calculator runs this arithmetic for your actual room dimensions rather than a rule of thumb.

Why H13 HEPA is the relevant stage

AIRE units carry several filtration and sterilisation stages, and it's worth being specific about which one matters for haze. PM2.5 is a mechanical filtration problem — particles need to be physically captured — so the relevant specification is H13 HEPA, which is rated to capture fine particulate at the 0.3 micron benchmark. UV-C and other active stages are built for airborne organisms, not smoke particulate, so they are not the reason to choose a unit during haze; the H13 stage is.

Matched to floor area, the AIRE range runs from the Fillo Plus (up to 30 m², CADR 300 m³/h, under 53 dB, H13 plus UV-C, Tuya WiFi control) through the Classic 400S (31–54 m², CADR 480 m³/h, seven-layer filtration stack) to the Pro 800S for larger clinic floors and open offices (56–96 m², CADR 800 m³/h, dual intake, castors for repositioning, a 26 dB sleep mode, and an onboard PM2.5 sensor useful for watching the room's own readings through a haze episode). A single desktop unit like the KJ100F can help at a reception counter but should not be treated as room coverage. Our technology page sets out how the filtration stack is built if you want the full stage-by-stage detail, and the full product range is listed separately for comparison.

Buy, or rent for the season

Haze is intermittent by nature, and that shapes the purchase decision. A clinic or office that only ever needs supplementary PM2.5 control during a haze episode is often better served by short-term rental than by a purchase that sits idle the rest of the year — rental includes delivery, filters and collection, and is arranged as commercial rental rather than a retail transaction. A site running purifiers year-round for general air quality management, on the other hand, is usually better off owning the equipment outright, with servicing arranged separately. Our rental-versus-buying comparison walks through both scenarios in more detail.

The one variable you cannot control is timing. Once the PSI starts climbing, demand for rental stock rises across Singapore within days, and units get allocated on a first-booked basis. If your clinic or office has a haze contingency plan on paper, the sizing and booking conversation is worth having before the season is actually underway, not once the readings are already high. We do not publish rental rates on this page — pricing depends on unit count, duration and delivery site, and is quoted once we know your rooms.

What we will not claim

We will not tell you that an air purifier reduces sick days, prevents infection, or makes a room's air "safe" — those are outcomes we cannot measure or guarantee, and we do not make them. What we can state is what the equipment is specified to do: capture particulate at the H13 HEPA standard, at a measured CADR, in a room of a given size. Any chamber-test figures we quote (for example, results against tested organisms under laboratory conditions) describe sealed-chamber conditions, not occupied clinic rooms, and we say so plainly rather than implying the same result happens in daily use. Our units carry an FDA Class 2 medical device listing held by the manufacturer — not FDA approval or certification, which is a different and stronger claim we do not make — alongside CE and RoHS marks and ISO 9001/14001 management systems. How we verify our claims sets out exactly what we can and cannot say and why.

Getting your rooms sized before the PSI moves

The most reliable way to avoid both under-sizing and last-minute scrambling is to have your rooms measured before haze season, not during it. For clinics specifically, our Clinic Air Report is a S$150 per-site visit covering a minimum of two rooms — every room is measured on site, and you receive a report by email within two working days, with a sized-right guarantee: if the specified unit doesn't reach the report's own air-change figure, we upgrade or add a unit at no extra cost. The Clinic Air Report page has the full detail, and our clinic air purifier guide covers waiting room and consultation room sizing beyond haze specifically. If your building isn't a clinic, our solutions overview covers office and preschool sizing along similar lines, or you can contact us directly to talk through your rooms ahead of the next haze episode.