Haze
Singapore experiences haze from time to time, usually caused by forest fires in the region. It can be made worse by dry seasons, changes in wind direction, and when rainfall is low.
Last updated 3 July 2025
The Pollutant Standards Index (PSI) measures the air quality and indicates the severity of haze. A PSI reading of 101 and above is deemed unhealthy.
The health impact of haze is dependent on one’s health status (e.g. whether one has pre-existing chronic heart or lung disease), the PSI level, and the duration and intensity of outdoor activity.
For healthy individuals, short-term exposure (i.e. over a few days) to haze will generally not cause any major health issues, other than irritation of the eyes, nose, and throat. N95 masks are not needed for such short-term exposure, like commuting from home to school or work. N95 masks are also not needed in an indoor environment.
In most cases, it is still safe to carry on with outdoor activities. However, you should drink plenty of water to stay hydrated, and individuals with existing chronic heart and lung conditions should ensure that medications are on hand and readily available.
Reducing outdoor activities and physical exertion can help limit the ill effects from haze exposure. Healthy individuals who need to be outdoors for several hours when the air quality is in the hazardous range (PSI >300) may reduce exposure by wearing an N95 mask with a good fit. Elderly, pregnant women and people with severe lung or heart problems should consult their doctor as to whether they should use the N95 mask if they have to be outdoors for several hours.
While this health advisory provides general precautionary advice, each individual’s reaction to pollutants may vary. The amount of physical activity or exertion that can be performed outdoors during haze periods also differs according to an individual’s health status or capacity. Persons who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical advice.
MOH Health Advisory for the General Public:
24-Hour PSI Descriptor | 0-50 Good | 51-100 Moderate | 101-200 Unhealthy | 201-300 Very Unhealthy | >300 Hazardous |
|---|---|---|---|---|---|
HEALTHY PERSONS | Normal Activities | Normal Activities | Reduce prolonged or strenuous outdoor physical exertion | Avoid prolonged or strenuous outdoor physical exertion | Minimise outdoor activity |
ELDERLY, | Normal Activities | Normal Activities | Minimise prolonged or strenuous outdoor physical exertion | Minimise outdoor activity | Avoid outdoor activity |
PERSONS | Normal Activities | Normal Activities | Avoid prolonged or strenuous outdoor physical exertion | Avoid outdoor activiy | Avoid outdoor activity |
Note: 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
