Central Singapore’s 24-hour PSI hit 173 on 9 October 2026, a new high for the year, with hourly PM2.5 (particulate matter) readings elevated in every region of the island, from 87 in the north to 142 in the central area, according to reporting from The Straits Times. Most haze advice stops at telling you which number to check before stepping outside.
But people spend the overwhelming majority of a hazy day indoors, at home, in the office, in the classroom, so haze-proofing your home matters as much as deciding whether to mask up outdoors. Closing the windows is step one, not the whole plan. Here is what actually cuts the fine particles that get through anyway, and what to prioritise depending on who you are sheltering.
Key Takeaways
- Central Singapore’s PSI reached 173 on 9 October 2026, a 2026 high, with PM2.5 elevated across all five regions.
- Closing windows reduces but does not eliminate indoor PM2.5; fine particles still work their way in through gaps and settle on surfaces.
- Singapore’s own preschools and schools are required to keep air purifiers running in enclosed rooms once the PSI reaches an unhealthy level; the same principle applies at home.
- One UK study found that a HEPA air purifier cut bedroom PM2.5 by 45 percent within 90 minutes of being switched on, though this is a single modelling study, not a clinical trial.
- Frying, candles, incense and indoor smoking add particles faster than most purifiers remove them, so cutting these matters as much as adding a purifier.
Why Shutting the Windows Isn’t the Whole Answer
PM2.5, the fine particulate matter that dominates haze, is small enough to penetrate deep into the lungs, and a 2016 review in the Journal of Thoracic Disease notes it is the main health hazard among haze components for this reason. The same review points out that most people, particularly the elderly, spend 80 to 90 percent of their day indoors, so indoor exposure drives most of a family’s total haze exposure over a bad week. Sealing a home slows the inflow, but it does not stop it.
What Actually Clears the Air Inside
The National Environment Agency’s haze advisory recommends a short list of indoor measures: keep windows and doors shut during unhealthy stretches, set air-conditioning to recirculation mode rather than drawing in outside air, run a true HEPA air purifier, and avoid adding particles indoors through smoking, candles, incense or frying. A 2020 University College London study that monitored 18 flats over six months found that a home air purifier produced a 45 percent reduction in bedroom PM2.5 within 90 minutes of continuous use, according to the authors’ RoomVent conference paper. That is a single modelling study, not a randomised trial, so treat the figure as indicative rather than definitive.
Indoor Haze Measures at a Glance
| Measure | What it does | What the evidence shows |
|---|---|---|
| Close windows and doors | Blocks the bulk inflow of outdoor smoke | Reduces but does not eliminate PM2.5 entry through gaps |
| Air-con on recirculation mode | Stops the unit from drawing in outside air | Only effective if the unit’s outdoor air intake is also closed |
| HEPA air purifier, sized to the room | Filters fine particles already indoors | Around 45% median bedroom PM2.5 reduction within 90 minutes in one UK study |
| No smoking, candles or frying indoors | Removes added indoor particle sources | Can offset filtration gains if ignored, per the 2016 review |
What To Actually Do, Depending on Who’s at Home
For families with young children or preschoolers, Singapore’s official policy offers a useful model: preschools and schools keep air purifiers running in at least one enclosed room where children can shelter. Parents should also keep inhalers and other prescribed medication readily available.
If elderly parents live with you, encourage them to spend most of the day in the room with the purifier. The effects of haze can take time to appear in older adults, and early signs of worsening heart or lung conditions can be easy to miss.
For someone with asthma or COPD, the priorities are straightforward: keep medication accessible and follow their action plan. Tracking symptoms against air-quality data may help identify personal triggers, but it should inform, not replace a conversation with a doctor. Even if no one at home is at higher risk, running a purifier during the worst hours remains a sensible, low-effort precaution.
Frequently Asked Questions
Do I need an air purifier in every room?
Not necessarily. The clearest evidence so far focuses on the room where someone spends the most time, typically a bedroom overnight, since that is where cumulative exposure adds up fastest for children and the elderly.
Is closing the windows enough on its own?
No. Fine particles still infiltrate through small gaps and settle on furniture and floors, which is why official advisories pair window closure with active filtration rather than treating it as sufficient on its own.
What if I don’t own an air purifier?
Set air-conditioning to recirculate, stop frying and smoking indoors, and keep any higher-risk family member in the room that is most sealed from outside air until you can get one.
When should the whole family just stay indoors?
The Bottom Line
With central Singapore’s PSI already past 170 this week, closing the windows buys time but is not the full answer. Pair sealed windows and a recirculating air-conditioner with a properly sized HEPA purifier running where your family spends the most time, and first strip out indoor sources like smoking, candles, and frying. The research behind the exact numbers is still developing, but the approach mirrors what Singapore’s own schools and preschools are already required to do, which makes it a sound default for any home right now.
Editorial Note
This article is intended for general educational purposes only and does not constitute medical advice. Individual sensitivity to haze varies with age, underlying heart or lung conditions, and duration of exposure. Consult a doctor before changing how you manage a chronic respiratory or cardiac condition during haze season, and seek prompt medical attention for severe or worsening symptoms such as breathlessness, chest discomfort or persistent wheezing.
Sources
- The Straits Times/ANN. “Haze in Singapore: PSI Hits 173 in Central Region, a New High for 2026.” The Star, 2026. https://www.thestar.com.my/aseanplus/aseanplus-news/2026/10/09/haze-in-singapore-psi-hits-173-in-central-region-a-new-high-for-2026
- National Environment Agency Singapore. “Singapore Government Agencies Implement Measures to Mitigate Impact of Haze.” National Environment Agency Singapore, 2026. https://www.nea.gov.sg/media/news/news/index/singapore-government-agencies-implement-measures-to-mitigate-impact-of-haze-Aug2026
- Fullerton Health Singapore. “Advisory on Haze Conditions in Singapore.” Fullerton Health Singapore, 2026. https://www.fullertonhealth.com/sg/advisory-on-haze-conditions-in-singapore/
- Zhang, S., Li, L., Gao, W., Wang, Y., Yao, X. “Interventions to Reduce Individual Exposure of Elderly Individuals and Children to Haze: A Review.” Journal of Thoracic Disease, 2016. https://jtd.amegroups.org/article/view/6490/html
- Cooper, E., Wang, Y., Stamp, S., Mumovic, D. “Health Benefits of the Use of Portable Air Purifiers That Reduce Exposure to PM2.5 in Residences: The Case of Childhood Asthma in London.” RoomVent 2020 (UCL Discovery), 2020. https://discovery.ucl.ac.uk/id/eprint/10129219/