Every few years, smoke from fires in the region drifts across Singapore and turns a clear sky into a grey, bitter-smelling blur. For most people the haze is an annoyance, but for children, older adults and people with heart or lung conditions it can be a real health risk.
In this article we will discuss where haze comes from, how to read the official air quality readings, which masks and home measures help, and how to plan school, work and exercise when the air turns poor.
Haze and where it comes from
Haze is a mix of tiny particles and gases suspended in the air, and it reduces visibility as well as air quality. In Singapore the severe episodes are usually linked to open burning and peat or forest fires in neighbouring parts of the region. These fires are often started to clear land, and they spread more easily in dry weather. Smoke from them can travel for hundreds of kilometres before it reaches us.
Timing and wind direction explain why haze arrives when it does. The drier months in the region commonly fall in the middle of the year, and during the southwest monsoon season winds can carry smoke towards Singapore. A change in wind direction can clear the air within hours, which is why readings can swing from good to unhealthy and back in a single day. Rain also washes particles out of the air, though it does not reliably end a haze episode.
Local sources add to the problem on top of what drifts in. Traffic, industry, construction dust and open burning at home all contribute, and these sources are present all year, not only in the haze season. The NEA monitors air quality across the island and reports readings by region. The agency is also involved in regional discussions among neighbouring countries to reduce the fires, since the main cause lies outside Singapore’s borders.
Not every grey sky is haze. Humid weather, clouds and fog can mimic its appearance, and a smoky smell can come from a nearby local fire. The only reliable way to tell is to check the official readings, which are updated frequently and are free to view. Making that check a habit during the dry months saves you from guessing.
Haze is not new to the region, and the pattern repeats in cycles. Some years are mild, with only a few hazy days, and others bring long spells that affect daily life. Weather patterns that bring dry conditions to the neighbouring islands tend to raise the risk of fires. This is why it is wise to prepare every year and not only after a bad episode appears in the news.
Regional cooperation is part of the long-term answer. The countries of Southeast Asia have an agreement on transboundary haze pollution, and they share information and work on fire prevention and response. Progress is gradual, and fires still occur when conditions are dry. Residents cannot control this, so the sensible response is to keep informed and be ready.
Reading the PSI and PM2.5 numbers
The Pollutant Standards Index, or PSI, is the headline number the NEA publishes for the air. It converts readings of several pollutants into a single score, and the score is grouped into bands that are widely published. The usual bands run from good at the low end, through moderate and unhealthy, to very unhealthy and hazardous at the top. Each band comes with health advice from the Ministry of Health, or MOH, so the number is meant to be acted on and not just observed.
The PSI is normally given as a 24-hour figure, which smooths out short swings by looking at the past day. This is useful for the general picture but can lag behind sudden changes. For that reason the NEA also publishes hourly PM2.5 concentrations, which show what is happening right now. Many people check both, using the 24-hour PSI for the overall category and the hourly PM2.5 for deciding whether to step outside in the next hour.
PM2.5 refers to particles with a diameter of 2.5 micrometres or less, which is far thinner than a strand of hair. These particles are the main concern in haze because their small size lets them travel past the nose and throat into the lungs. Some can pass into the bloodstream, which is why haze is linked to heart problems as well as breathing problems. Larger particles are mostly caught in the nose and upper airway, so they cause less trouble deeper down.
The simple way to read the figures is to match your own situation to the band. The table below shows a practical way to think about each band. Confirm the exact ranges and advice on the NEA and MOH websites, since the details can be updated.
| Air quality level | General meaning | Sensible approach for most people | Extra care for vulnerable groups |
| Good | Air is clean | Normal activities | None needed |
| Moderate | Air is acceptable | Normal activities | Watch for symptoms if very sensitive |
| Unhealthy | Air is poor for many | Reduce long or strenuous outdoor activity | Stay indoors where possible and keep medication handy |
| Very unhealthy | Air is poor for everyone | Avoid outdoor exertion | Remain indoors and contact a doctor if symptoms appear |
| Hazardous | Air is a serious risk | Minimise time outdoors | Stay indoors and seek medical advice early |
Learning to read the numbers in daily life takes only a few minutes. Look at the band first, then at the hourly PM2.5 reading, and then at the trend over the past few hours. If the figures are climbing, plan to be indoors for longer. If they are falling, wait for the improvement to hold before you open windows or resume outdoor plans.
Keeping informed is easier than most people think. The NEA publishes readings on its website and through its mobile app, and news outlets repeat the main figures when conditions change. Choose one or two trusted sources and check them at fixed times, such as in the morning before school or work. Avoid forwarded messages and social media rumours, which often exaggerate or contradict the official picture.
Health effects and who is most at risk
Haze irritates the eyes, nose, throat and airways, and the first signs are often mild. Common complaints include a dry or sore throat, a runny or blocked nose, watery or itchy eyes, coughing and a mild headache. These usually settle once the air improves, and most healthy adults recover without treatment. If you do feel unwell, resting indoors, drinking water and rinsing your eyes with clean water or saline can bring relief.
Certain groups are more vulnerable, and for them the same air can cause more serious problems. People with asthma may find that wheezing and coughing worsen and that their reliever medication is needed more often. Those with chronic lung conditions such as COPD, and people with heart disease, can see their symptoms flare. Children breathe faster for their body size and spend more time active outdoors, while older adults often have underlying conditions that make them less able to cope.
Pregnant women are often advised to be careful as well, since poor air can add strain on the body at a time when it is already working harder. If you are pregnant, talk to your doctor about what is sensible for you. There is no need to panic, but there is value in being prepared. A simple plan agreed in advance is better than a decision made in distress.
Some signs mean you should seek medical help rather than wait. These include chest pain or tightness, severe breathlessness, wheezing that does not respond to your usual medication, fainting, a racing or irregular heartbeat, or symptoms that keep getting worse. Call 995 in an emergency, and otherwise see a general practitioner or a polyclinic. People with long-term conditions should follow their doctor’s action plan and keep enough medication at home for the haze season.
The effects of haze depend on how long you are exposed and how intense the exposure is. A short walk to the train station on a moderate day is very different from a long outdoor run on an unhealthy one. Most healthy people can handle brief exposure with little trouble. The sensible aim is to cut the total time and effort outdoors when the air is poor, not to avoid all contact.
Eyes and skin can also feel the effects of smoky air. Contact lens wearers often find that their eyes become dry or sore, so switching to glasses for a few days can be more comfortable. Rinse the eyes gently with clean water or sterile saline instead of rubbing them. Showering and changing clothes after a long spell outdoors removes particles from the skin and hair. If eye pain, redness or blurred vision lasts, see a doctor.
Masks that work and masks that do not
A mask is only useful if it filters the particles that matter and fits your face. Fine haze particles are small, so the mask must be designed to filter them. An N95 respirator, or an equivalent standard such as FFP2 or KN95 in other markets, is made for that purpose, and the rating describes how well it filters small particles in a test. Standards and labels differ by country, so look for clear markings and buy from a reliable supplier.
Ordinary surgical masks and cloth masks do not do the same job. A surgical mask is made to reduce the spread of droplets from the wearer and to protect against splashes, but it fits loosely and is not designed to filter fine smoke particles. A cloth mask offers even less. Wearing them can feel reassuring, but in dense haze they give limited protection against PM2.5.
Fit matters as much as the rating. A respirator that leaves gaps around the nose or chin lets unfiltered air leak in, so the benefit falls sharply. Check that it covers the nose and chin, that the straps sit snugly, that the metal strip is pressed to the shape of your nose, and that no air escapes around the edges when you breathe out. Facial hair under the seal can also cause leaks.
Wearing a respirator is not comfortable for everyone, and it adds a little breathing effort. People with heart or lung conditions, pregnant women and anyone who feels dizzy or short of breath in a mask should ask a doctor before using one for long periods. Respirators are generally not designed for small children, and a poorly fitting one can be worse than none, so for young children the safer approach is to keep them indoors. Masks are single-use or limited-use items, so replace one when it becomes damp, damaged or hard to breathe through, and follow the maker’s instructions.
Many people ask whether it is worth wearing a respirator for short trips. The answer depends on the air quality band, the length of the trip and your own health. For a quick walk on a moderate day, most healthy adults do not need one. When the air is unhealthy or worse, or if you have a heart or lung condition, a well-fitted respirator is a reasonable precaution for essential trips.
Buying and storing masks needs a little thought. Choose products from reliable sellers, and check the packaging for the standard and the intended use. Keep a few spare masks in places that are easy to reach, such as the front door, the bag you take to work and the car. Store them in a clean, dry bag, away from dust and moisture, and avoid sharing them between family members.
Keeping the air cleaner at home
Your home is the best place to shelter, but it only helps if you manage the air inside. Close windows and doors during poor air quality, and seal obvious gaps if you can. Air-conditioning that recirculates indoor air is better than opening windows for fresh air, but it should not draw in outside air if you can avoid it. If your unit has a fresh air setting, switch it off while the air is poor.
An air purifier with a suitable filter can reduce fine particles indoors. Look for a model with a high-efficiency filter, which is commonly called a HEPA filter, and check that its capacity matches the size of the room. A small purifier in a large living room will do very little, so place it in the room where you spend the most time, such as a bedroom. Follow the manufacturer’s advice on cleaning and filter replacement, because a clogged filter loses effectiveness.
Avoid creating more pollution indoors. Smoking, burning incense or joss sticks, lighting candles and frying at high heat all add particles to the air. If you cook, use the extractor fan or hood where there is one, and choose methods that produce less smoke. Vacuum cleaners without a good filter can stir up dust, so damp mopping and wiping surfaces is often a gentler way to clean.
Keep a few essentials ready before the haze season begins. Stock enough medication, a supply of masks, saline eye drops, and a thermometer in case someone is unwell. Keep the contact details of your doctor handy and make sure everyone in the household knows where these items are kept. If you rely on a purifier, check its filters in advance, since stores can run low during a bad episode.
Cooking and cleaning habits matter more than most people expect. Steam and smoke from the kitchen can push indoor particle levels higher than the air outside. Avoid frying or grilling at high heat when the air is poor, and consider simpler meals. Keep rubbish bins covered, and avoid burning anything indoors or on the balcony, as open burning is also a source of the problem.
Homes differ in how well they keep the haze out. Older flats with louvred windows and gaps around doors leak more than newer units with tight seals. Simple measures help, such as closing all windows, drawing curtains over gaps and placing a rolled towel at the base of a door. Choose a single room, such as a bedroom, to be the cleanest space, and keep the door shut so the purifier can work on a smaller volume of air.
Planning school, work and exercise during haze
Schools, workplaces and families make many decisions during a haze episode, and a calm plan avoids confusion. The Ministry of Education, or MOE, issues guidance on how schools adjust outdoor activities and what they do when air quality worsens. This usually involves reducing or moving strenuous outdoor activities indoors as the readings rise. Parents should check school communication channels and follow instructions rather than relying on rumour.
For workers, the Ministry of Manpower, or MOM, publishes guidance for employers on protecting staff who work outdoors. Employers are expected to assess the risk, adjust work and rest patterns and provide suitable protective equipment as conditions worsen. If you work outdoors, speak to your supervisor about the arrangements and report symptoms early. Do not push through chest pain or severe breathlessness for the sake of finishing a shift.
Exercise needs more thought than people expect. Breathing hard draws more polluted air deeper into the lungs, so strenuous outdoor exercise is the activity most affected when the air is poor. On a poor air day, move your workout indoors, choose a lighter activity or rest. When readings improve, return to your usual routine gradually.
Travel and daily errands can be adjusted too. Keep outdoor trips short, and combine errands into one outing rather than several. When driving, keep the windows closed and use the recirculation setting for the air conditioning. If your plans involve a long outdoor event, check the forecast of air quality beforehand and have a backup plan indoors.
Employers and organisers also have a role in keeping people safe. Event organisers may postpone or move outdoor events when the readings rise, and sports bodies often have their own rules. If you manage a team, a class or a group of seniors, decide in advance at what reading you will change the plan. Put the rule in writing and tell everyone, so that nobody has to argue about it on the day.
Pets also feel the effects of poor air, though they cannot tell you how they feel. Keep dogs and cats indoors as much as possible, shorten walks and avoid strenuous play outdoors. Watch for coughing, sneezing, watery eyes or lethargy, and speak to a vet if the signs persist. Birds and small animals are sensitive to smoke, so keep their enclosures away from open windows and kitchens.
Looking after children, older adults and people with long-term conditions
Children need special consideration because their bodies are still developing and they are often active outside. On days when the air is unhealthy, keep them indoors and choose quiet activities such as reading, drawing or board games. Watch for coughing, wheezing or complaints of a sore throat, and let the school know if your child has asthma. Make sure that a child’s reliever inhaler and spacer are within reach and have not expired.
For older adults, the main risks are existing heart and lung conditions and the difficulty of recognising early symptoms. Check on elderly relatives and neighbours, especially those who live alone. Make sure they have medication, water and a way to call for help. If they use a purifier or air-conditioning, confirm that it is working before the air turns poor.
People with asthma should follow a written asthma action plan agreed with their doctor. This usually lists daily controller medication, reliever use and the signs that mean they should seek urgent help. Haze can trigger attacks even in people whose asthma is usually well controlled. Keep medicines within date and carry the reliever when you leave home.
People with heart disease or lung disease should talk to their doctor about what to do during the haze season. This may include adjustments to medication, a plan for symptoms and advice on when to seek care. Do not stop or change medication on your own. If you notice new chest pain, breathlessness at rest or swelling in the legs, treat it as a medical matter rather than a haze complaint.
Communities can help one another through a haze episode. Neighbours can check on older residents, community centres can share information, and family members can help with errands so that vulnerable people do not need to go out. If you volunteer or work with seniors, make a list of who needs a phone call and keep a record of those who have supplies. Small acts of care reduce the burden on both households and clinics.
Keep a short list of the key points on the fridge or in a phone note so that anyone in the household can follow it. Include the PSI band at which you stay indoors, the contact number of your family doctor, the location of masks and medication, and the steps for children and older relatives. Review the list at the start of each dry season. A written plan is easy to share with relatives, helpers and neighbours who may be caring for someone in your family.
Final Thoughts
The best time to prepare for haze is before the air turns bad. Spend a short time this week on the practical steps below. You will cope far better when an episode arrives.
First, bookmark the NEA air quality page or app, and check it when the sky looks hazy or the dry season begins. Second, find out which members of your household are vulnerable, and ask their doctors what to do. Third, buy a few N95 or equivalent respirators for adults, and practise fitting them.
Fourth, check your medication, your air purifier filter and your supplies of eye drops and water.
When the air quality worsens, follow a simple routine. Read the PSI and the hourly PM2.5, stay indoors with windows closed if the band is unhealthy or worse, and cut back on strenuous outdoor activity. Keep a record of any symptoms, and contact your doctor if they persist. Follow the guidance from MOH, MOE and MOM, because their advice is updated as conditions change.
Keep the situation in perspective as well. Most haze episodes pass within days, and healthy adults generally recover without lasting problems. The aim is to protect the people who are most at risk and to avoid unnecessary exposure for everyone else. Confirm the current bands, advice and school or work arrangements on the official NEA, MOH, MOE and MOM websites, since the details can change.
