This article is reviewed by Dr. Leong Choon Kit and is intended for general informational purposes only. It does not constitute medical advice. Please consult your GP or a qualified health professional before making changes to your diet, particularly if you have an existing medical condition.
How to Protect Yourself from Haze in Singapore
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PM2.5 particles can enter your home and linger in the air — short exposure and being indoors aren’t as safe as most people think.
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Early mornings and cool nights have higher ground-level particles, not lower — avoid outdoor exercise at these times during haze.
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Surgical masks don’t filter PM2.5; only a properly fitted, pharmacy-bought N95 will protect you outdoors.
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Excess phlegm is the most dismissed symptom — in vulnerable individuals, it can progress to asthma attack or pneumonia.
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If you’re breathless, feverish, or your pulse oximeter reads below 95%, stop managing at home and see a doctor.
Every year, as haze settles over Singapore, most people glance at the sky, perhaps reach for a mask, and carry on with their day. It’s a familiar inconvenience — but according to Dr Leong, that casual attitude is precisely the problem.
Haze is far more medically significant than most Singaporeans appreciate, and the habits people rely on for protection are often either wrong or dangerously incomplete.
Dr Leong, drawing from his direct clinical experience, explains what haze actually does to your body, who is most at risk, and what you should genuinely be doing — and stopping — to protect yourself and your family.
1. What Is Haze and Why Is It Dangerous?
Haze is not simply a weather condition or a visibility problem. At its core, it is an event where enormous quantities of fine particles — primarily from burning vegetation, industrial emissions, and smoke — become suspended in the atmosphere. The most medically significant of these are particles measuring 2.5 micrometres or less in diameter, known as PM2.5.
What makes PM2.5 so dangerous is its invisibility and persistence. These particles are small enough to remain airborne for extended periods, drifting through the environment long after the smoke that generated them has dissipated.
They are also small enough to pass through many standard filtration barriers — including the surgical masks most people instinctively reach for.
But the danger doesn’t stop at the front door. A common and false comfort is the assumption that being indoors provides safety. In reality, PM2.5 particles can penetrate building envelopes, seeping through gaps around windows and doors and gradually degrading the air quality inside homes and workplaces.
Understanding this is the foundation of any genuinely effective haze protection strategy.
2. What Haze Does to Your Body — What the Doctor Actually Sees in Clinic
During haze periods, the presentation of patients at Mission Medical Clinic follows a consistent and telling pattern. The most common presenting complaints are runny nose, cough, sore throat, phlegm, and sore eyes.
Beyond these, some patients present with low-grade fever and signs of dehydration — a connection many would not instinctively draw to the air quality outside.
The dehydration link is particularly significant for elderly patients. When the body is under stress from environmental irritants, it can manifest in ways that appear entirely unrelated to the lungs.
Elderly patients, the doctors note, may experience constipation and urinary tract infections as secondary consequences of dehydration brought on by haze exposure.
These are presentations that could easily be attributed to other causes and treated in isolation — without anyone considering the haze as the underlying driver.
“The most often ignored symptom is the excess mucus and phlegm. Most people will write this off as insignificant.” – Dr Leong Choon Kit
This dismissal can be a serious mistake. In immunocompromised individuals and those with hypersensitive conditions, persistent phlegm and mucus build-up can progress over time into something far more serious.
The more common complications seen clinically include asthma attacks and pneumonia — outcomes that could have been prevented had the early warning signs been taken more seriously.
For patients already living with chronic conditions, the picture is more acute. Those with pre-existing heart or lung disease — including asthma, chronic obstructive pulmonary disease (COPD), and cardiovascular conditions — face a heightened risk during haze episodes.
Clinically, these patients present with asthmatic attacks, chest infections, and pneumonia. Some also show rises in their heart rate and blood pressure, a reminder that haze is not exclusively a respiratory event.
Across all these patients, a pattern emerges: they are more tired than usual despite rest, breathless, coughing more, and experiencing chest pain. These are not mild inconveniences — they are signals that the body is under significant physiological stress.
3. Understanding PSI Levels — And What They Mean for You
Singapore’s Pollutant Standards Index (PSI) is the primary tool used to communicate air quality to the public in real time. Understanding it properly — rather than relying on impressions — is essential.
The two extremes are straightforward. A PSI reading below 50 represents absolutely normal air quality, and life can go on as usual without any particular precaution. At the other end, a PSI above 200 crosses a threshold that studies show is genuinely harmful.
At this level, the vulnerable — the very young, the elderly, those with lung and heart diseases, and those with hypersensitivities — are at meaningful risk and should be taking active protective measures.
Between those poles, the picture is more nuanced. Any number in between is a shade of its severity, and one can adjust accordingly — taking into account personal health status, duration of planned outdoor activity, and the specific conditions of the day. The PSI is not a binary switch but a sliding scale, and individual calibration matters.
Real-time PSI readings are available through the National Environment Agency’s haze website and the myENV app, which provides hourly updates and is the most practical tool for day-to-day monitoring.
4. Who Is Most at Risk?
While haze has some effect on virtually everyone exposed to it, certain groups carry a disproportionately higher burden of risk. Understanding who falls into these vulnerable categories is important both for the individuals themselves and for the families and caregivers around them.
The primary vulnerable groups are the very young, the elderly, pregnant women, and those with pre-existing chronic conditions — particularly lung diseases such as asthma, COPD, bronchitis, and sinusitis, as well as heart disease.
Individuals who are immunocompromised, whether through illness or medication, also face elevated risk because their bodies are less equipped to manage the inflammatory response that fine particle inhalation triggers.
For these groups, the PSI threshold for meaningful precaution is lower than for healthy adults. Vulnerable individuals should be wearing N95 masks outdoors when PSI surpasses 200, rather than waiting for the 300 threshold that applies to the general healthy population.
They should also be actively limiting outdoor time during peak haze conditions and monitoring their symptoms more vigilantly than they might otherwise.
The clinical reality is that for patients already managing heart or lung conditions, a haze episode is not an inconvenience — it is a genuine medical risk event that can trigger hospital-level presentations if not managed carefully.
5. The One Thing Most Patients Get Wrong
Of all the misunderstandings surrounding haze, there are a handful that doctors encounter repeatedly in the clinic — and that collectively put a great many people at unnecessary risk.
The first and most common is simple dismissal. Most patients will ignore the haze and hope that it will not affect them at all. They believe they will not be the unlucky ones. This optimism bias is understandable but medically unfounded.
PM2.5 does not discriminate based on perceived luck, and cumulative exposure — even at moderate PSI levels — can tip individuals with underlying vulnerabilities into acute illness.
The second misconception is the idea that brief outdoor exposure is harmless. Many people believe that by just exposing themselves for a short while, they would not be badly affected. The reality is that PM2.5 particles are so small and so persistent in the air that even relatively short exposure carries risk, particularly for vulnerable individuals.
“What is not understood fully is that the haze particles are very small and usually less than PM2.5. So they can stay in the air for a long time and also they may even enter our homes.” – Dr Leong Choon Kit
The third — and perhaps most counterintuitive — misconception relates to timing. Most people assume that when the weather is cooler, the haze is less severe, and they choose to exercise outdoors during the early morning or at night. The reality is the opposite.
During cooler periods, particles tend to bind with the dew and moisture in the air, becoming heavier as a result. This causes them to descend closer to ground level — precisely where people are breathing.
The early morning and evening, the times most Singaporeans favour for outdoor exercise, are in fact the periods of highest ground-level particle concentration during haze events.health and comfort can remain top priorities, even when the air quality suggests otherwise.
6. How to Protect Yourself Outdoors — N95 Masks Done Right
When outdoor exposure is unavoidable during haze conditions, the right mask is not a minor detail — it is the difference between meaningful protection and a false sense of security.
Standard surgical masks, the kind most people have become familiar with, are not designed to filter fine particulate matter and will not provide adequate protection against PM2.5 during haze episodes.
Only certified N95 masks provide the level of filtration required.
Choosing Your Mask
For those purchasing in Singapore, N95 masks sold at pharmacies are generally from reputable brands that have been certified by the relevant authorities. This is the recommended purchasing channel.
Those sold online, however, may bypass the usual quality checks and quality assurance processes. As the doctors put it, it is a case of caveat emptor — the buyer must do their own due diligence when purchasing through less regulated channels.
Getting the Fit Right
A certified mask is only as effective as its fit. For N95 masks, there is usually a need to check the seal against the face — any gap around the nose or jaw allows unfiltered air to enter.
This is particularly important for children and elderly patients, whose facial proportions may make standard adult sizing a poor fit.
The good news is that help is readily available: members of the public can consult their family physicians, nurses, or pharmacists to have their mask fit assessed and corrected.
Using and Disposing Safely
When putting on the mask, always start with clean hands. Position the mask over the nose and mouth, press the metal strip firmly to the shape of the nose to create a seal, and check for gaps before heading out.
When removing it, avoid touching the front surface — use the ear loops and dispose of it immediately, then wash your hands. N95 masks should never be shared and should not be reused once soiled or distorted in shape.
7. Protecting Your Home Indoors
Given that PM2.5 particles can infiltrate indoor spaces, a passive approach to indoor air quality during haze is insufficient. Creating a genuinely protective indoor environment requires deliberate action across several fronts.
The most immediate step is to keep windows and doors closed as much as possible. This limits the volume of outdoor air — and the particles it carries — entering the living space. Air-conditioning is preferable to natural ventilation during haze periods, as it recirculates indoor air rather than drawing in outside air.
For those who want to go further, portable air purifiers fitted with HEPA filters can significantly reduce indoor particulate concentration, particularly in the rooms where family members spend the most time — bedrooms and main living areas.
It is also worth being mindful of indoor activities that themselves generate particles: smoking, burning incense or candles, and cooking at high heat all contribute to indoor air pollution and should be minimised during haze events.
When cleaning the home during haze periods, favour wet-cleaning methods — mopping and damp-wiping — over dry-dusting or vacuuming, which can disturb settled particles and reintroduce them into the breathing zone. Taken together, these measures can make a meaningful difference to the quality of the air your family is breathing at home.
8. Supporting Your Lung Health During Haze Season
Many patients arrive at the clinic during haze season looking for a supplement or medication to boost their lung resilience. The clinical reality is straightforward: there is no supplement that can enhance the lungs in the face of particulate exposure. No vitamin, herbal product, or health food provides meaningful protection against PM2.5 inhalation.
What does support respiratory health is more fundamental — and more within reach. Regular aerobic exercise (undertaken, importantly, indoors when PSI levels are elevated), quitting smoking, staying well hydrated, and getting adequate rest and sleep are all genuinely more useful than any supplement.
Hydration is particularly worth emphasising, given that dehydration is itself a documented downstream effect of haze exposure.
Advice for Patients on Respiratory Medications
For those already managing asthma or allergic rhinitis, haze season calls for a proactive rather than reactive approach. Patients should continue their regular preventor inhalers and nasal sprays without interruption — haze is precisely the kind of environmental trigger that these medications are designed to manage.
If symptoms begin to emerge or worsen, increasing the dose is appropriate, but this should be done thoughtfully. If a patient has increased their medication and still feels unwell, that is the signal to consult their family physician promptly rather than continuing to self-manage.
The broader principle here is one that applies across all aspects of haze management: prevention is always better than treatment, and early action almost always leads to better outcomes than waiting until symptoms become severe.
If you have unused or expired medicines at home, read our guide on how to dispose of old medication safely and responsibly.
9. When to See a Doctor
Knowing when to manage symptoms at home and when to seek medical attention is one of the most practically important judgements a person can make during a haze event. The clinical guidance is specific and worth knowing in advance.
Breathlessness and fever are the key differentiating symptoms. If either is present — particularly in combination — a clinic visit is warranted rather than a home remedy.
For households that have a pulse oximeter, it can be a useful tool for self-assessment: an oxygen saturation reading of less than 95% is not acceptable and requires medical attention.
“Anyone who has symptoms of cough, phlegm, fever, shortness of breath, headache and fever, please see their own family physician. Or when they are unsure, it is also wise to seek help.” – Dr Leong Choon Kit
Beyond those threshold symptoms, several other presentations should prompt a visit: persistent coughing or phlegm that does not improve, chest pain, unusual levels of fatigue, and any worsening of a pre-existing chronic condition.
For vulnerable groups — children, the elderly, pregnant women, and those with heart or lung disease — the bar for seeking medical attention should be set lower than for healthy adults.
The fundamental message is this: if you are unsure whether your symptoms warrant a visit, they probably do. Erring on the side of caution during haze events is rarely a mistake.
Family physicians are equipped to assess haze-related presentations quickly and effectively, and early intervention is almost always preferable to managing a complication that could have been prevented.
If you’ve recently had blood work done, our guide on abnormal blood test results can help you understand what the numbers may mean.
Conclusion
Haze in Singapore is not a background inconvenience to be stoically endured. It is an annual public health event that sends a predictable wave of patients through clinic doors — many of whom could have avoided their visit with better preparation and fewer misconceptions.
The clinical picture is consistent: the people who fare worst are those who underestimate their vulnerability, exercise outdoors at the wrong times, wear the wrong masks, and wait too long before seeking help.
The people who fare best are those who monitor PSI levels, protect their indoor air, use properly fitted N95 masks when necessary, keep up their preventive medications, and consult a doctor at the first sign of meaningful symptoms.
Haze may be beyond any individual’s control. But the response to it is not.
FAQ – How to Protect Yourself from Haze in Singapore
1) Is it safe to exercise outdoors during haze?
Not during elevated PSI. Avoid outdoor exercise when PSI exceeds 100. Importantly, never exercise in the early morning or at night during haze — particles bind to moisture and descend to ground level at those times, making air quality worse than it appears.
2) What PSI level should I start taking precautions?
Below 50 is normal — no action needed. Above 100, reduce outdoor activity, especially if you’re in a vulnerable group. Above 200, studies show genuine harm; vulnerable individuals should stay indoors and wear an N95 if they must go out.
3) Do N95 masks actually protect against haze?
Yes, but only if fitted correctly and purchased from a pharmacy. Online purchases may bypass quality checks. Surgical masks do not filter PM2.5 and offer no meaningful haze protection. If unsure about your fit, ask your GP, nurse, or pharmacist.
4) Can haze affect you indoors?
Yes. PM2.5 particles are small enough to penetrate through gaps in windows and doors. Keep windows shut, run an air purifier with a HEPA filter, and use wet-mopping rather than dry-dusting to avoid stirring settled particles back into the air.
5) Should I take supplements to protect my lungs during haze?
No supplement has been shown to enhance lung function during haze. Staying hydrated, getting enough sleep, and regular aerobic exercise (indoors) are more effective. If you have asthma or allergic rhinitis, continue your preventor inhaler — don’t wait for symptoms to appear.
6) When should I see a doctor for haze symptoms?
See a doctor if you have breathlessness, fever, or chest pain, or symptoms that aren’t improving. If you have a pulse oximeter, anything below 95% oxygen saturation warrants a clinic visit. When in doubt, go — early intervention is always better than waiting.
7) Are children and elderly people at higher risk?
Yes. The very young, elderly, pregnant women, and anyone with heart or lung disease should take precautions at lower PSI thresholds than healthy adults. Elderly patients in particular can develop dehydration-related complications like UTIs and constipation during haze — symptoms that can easily be mistaken for something unrelated.
Medically Reviewed
About the Experts
Reviewer
Dr Leong Choon Kit
MBBS, M.Med (Public Health), GDFM, MCFP(S), FCFP(S), FAMS (Family Medicine) — Adjunct Assistant Professor, Duke-NUS & NUS
Dr Leong Choon Kit is a family physician and public health advocate with extensive experience in primary care, public policy, and vaccination initiatives. He leads Tampines Family Medicine Clinic and the Class Primary Care Network, and co-authored Singapore's Adult Vaccination Guidelines. An Adjunct Assistant Professor at both Duke-NUS Medical School and NUS, he has spent over a decade mentoring pre-medical students across all three local medical schools and is deeply committed to nurturing the next generation of doctors.
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About the Writer
Writer
Timothy Leong
Writer, Content Editor & Marketing Specialist — MMC
Timothy Leong is the writer, content editor, and marketing specialist at MMC. With experience in writing and creating websites for local businesses, he makes sure that everything online runs smoothly.
