Is the haze back again? Let’s take precautions. Haze is an atmospheric condition where particles, smoke, dust and moisture suspended in the air, obscuring visibility. Slight haze usually disperses when the winds pick up strength. However, at times, it can linger for days or months. In Singapore, we may experience haze, particularly during the Southwest Monsoon Season (June - September).

Impact On Your Health

Asian man feeling unwell and is wearing a mask

Short-Term Effects of Haze

  • Among healthy individuals, short-term exposure (i.e. continuous exposure to unhealthy daily average PSI levels over a period of a few days) to high levels of haze particles may cause irritation of the eyes, nose, and throat. Such irritation resolves on its own in most cases.
  • Haze particles can affect the heart and lungs, especially in people who already have chronic heart or lung disease e.g. asthma, chronic obstructive pulmonary disease (COPD), or heart failure.
  • There may be up to 1-3 days of lag time between exposure to haze and health effects/symptoms.

Long-Term Effects of Haze

  • Singapore is not affected by the haze throughout the year. Any exposure is short-term in nature and such exposure may vary from year to year.
  • As international studies are based on long-term exposure to air pollution, there is little robust data on the longer-term effects of short-term exposure to haze like the pattern seen in Singapore.

Related: How to Buy a Mask That Fits

Protect Yourself by Understanding PSI

A meteorological Station Measuring Haze Particles

You are encouraged to use published PSI readings to plan your activities during hazy conditions. Reducing outdoor activities and physical exertion against escalating PSI values can help limit the ill effects from haze exposure.

The National Environment Agency (NEA) publishes two types of readings:

SI Reading

Use this to...


1 Hour PM 2.5 readings

Make decisions on immediate activities, such as going for an outdoor run.

The 1-hour PM2.5 concentrations reflect the PM2.5 levels averaged over one hour and can give you an indication of the current air quality.

24-hour PSI forecast

Plan for tomorrow’s activity

The existing scientific evidence supports the use of our health advisory for future planning.

The 3-hour PSI reading was phased out with effect from 7 Dec 2016

Plan your day in accordance to these activity guidelines:

24-hour PSI

Healthy Persons

Elderly, Pregnant Women & Children

Persons with Chronic Lung or Heart Disease

0 - 50

Normal activities

Normal activities

Normal activities

51 - 100

Normal activities

Normal activities

Normal activities

101 - 200

Reduce prolonged or strenuous outdoor physical exertion

Minimise prolonged or strenuous outdoor physical exertion

Avoid prolonged or strenuous outdoor physical exertion

201 - 300
(Very Unhealthy)

Avoid prolonged or strenuous outdoor physical exertion

Minimise outdoor activity

Avoid outdoor activity


Minimise outdoor activity

Avoid outdoor activity

Avoid outdoor activity


  • Prolonged = continuous exposure for several hours
  • Strenuous = involving a lot of energy or effort
  • Reduce = do less
  • Minimise = do as little as possible
  • Avoid = do not do

Related: When a Mask is a Must

What is MOH’s Advice to the Public?

Asian woman discuss with her doctor

Do adhere to the MOH haze health advisory. In most cases, it is still safe to carry on with outdoor activities. However, drinking plenty of water may help symptoms such as a dry or itchy throat.

Each individual’s reaction to pollutants may vary, and the amount of physical activity or exertion that can be performed differs according to your health status or physical capacity. Should you encounter symptoms or discomfort, please take additional measures to prevent further exposure.

Although the general advice to the public when the forecasted air quality is good or moderate (PSI≤100) is to maintain normal activities, vulnerable persons, especially those with chronic heart and lung conditions who develop symptoms or feel unwell should seek medical attention promptly. Individuals with existing chronic heart and lung conditions should ensure that your medications are on hand and readily available.

What are some Practical Tips For Households to Reduce Exposure to Haze Particles at Home?

Closing Windows

Practical tips to reduce indoor exposure to haze particles at home during a haze episode include:

  • When the outdoor air quality appears to be worsening, close doors and windows. This will help to reduce the rate of haze particles entering the home.
  • Stay indoors and reduce physical activities.
  • Minimize activities that can produce indoor air pollutants in enclosed spaces, e.g. smoking.
  • Re-open the windows and doors in the home when the outdoor air quality improves.
  • Wet-cleaning methods (e.g. mopping or wiping) generally do not produce dust (unlike dry-dusting or vacuuming) and can be performed to remove settled dust.
  • Fans or air-conditioners may be used for air circulation and cooling. If the air-conditioner draws in unfiltered air from outside (e.g. window units), close the outdoor air intake opening.
  • Portable air purifiers can be used to further reduce the indoor particle level.

Protect Yourself Outdoors

When you have to be outdoors for several hours, an N95 mask can help filter out haze particles, including PM2.5 particles. Here’s a guide:

If you...

Wear an N95 mask when...

Are healthy,

PSI >300

Have chronic lung or heart disease,

PSI > 200

Are elderly or pregnant,

Both the NIOSH-certified N95 masks and the EN-149 masks are designed to reduce a wearer’s respiratory exposure to airborne contaminants such as particles, gases or vapours.

Do note that N95 masks are not needed for short exposure, like commuting from home to school or work, travel from bus-stop to shopping mall. N95 masks are also not needed in an indoor environment.

Follow these tips when buying and using an N95 mask:

  • For best effect, N95 masks need to be fitted properly for each user. To check for proper fit, please check that the available mask is appropriately sized and covers the nose and mouth comfortably without a leak
  • Make sure to follow these 6 steps when putting on the mask
  • Reuse the N95 mask if necessary, but do not share it
  • Change the mask whenever it gets soiled or distorted


  • The use of N95 masks increases effort in breathing and reduces air intake. Take a break from using it if you feel uncomfortable. Consult a doctor if you’re unsure whether you should use one.
  • Normal surgical masks are not effective in filtering fine particles (i.e. tiny particles that are 2.5 microns or less in width), although they can reduce the discomfort caused by haze by providing a barrier between the wearer’s nose and mouth, and larger irritant particles in the air.

Resources and Useful Links

You can get live updates on PSI readings on:

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