When the air turns hazy, the training call is not a vibe check. HealthHub’s haze guide, last reviewed on 27 October 2026, splits the decision into two clocks: the 1-hour PM2.5 reading for what you do in the next hour, and the PSI forecast for the next day.
Next hour: read 1-hour PM2.5
MSE and MOH’s personal guide uses four bands.
Band 1 (Normal, 0 to 55 µg/m³): continue with normal activities.
Band 2 (56 to 150 µg/m³): healthy persons reduce strenuous outdoor activity for the next hour; vulnerable persons avoid strenuous outdoor activity for the next hour.
Band 3 (High, 151 to 250 µg/m³): healthy persons avoid strenuous outdoor activity for the next hour; vulnerable persons avoid all outdoor activity for the next hour and may wear a mask to cut exposure.
Band 4 (Very High, 251 µg/m³ and above): healthy persons minimise all outdoor activity for the next hour and may wear a mask; vulnerable persons avoid all outdoor activity for the next hour and may wear a mask.
Vulnerable persons on the page include the elderly, pregnant women, children and people with chronic heart or lung disease. The guide is not a prescription; short-term throat or eye irritation in the general population is expected to ease after leaving the exposure.
Next day: read the PSI forecast
For sessions that last several hours, HealthHub points to the PSI forecast and its health advisory.
PSI 0 to 50 is Good and 51 to 100 is Moderate: normal activities for healthy persons, older adults, pregnant women, children and those with chronic lung or heart disease.
PSI 101 to 200 (Unhealthy): healthy persons reduce prolonged or strenuous outdoor physical exertion; older adults, pregnant women and children minimise it; persons with chronic lung or heart disease avoid it.
PSI 201 to 300 (Very Unhealthy): healthy persons avoid prolonged or strenuous outdoor exertion; older adults, pregnant women and children minimise outdoor activity; those with chronic lung or heart disease avoid outdoor activity.
Above 300 (Hazardous): healthy persons minimise outdoor activity; the other groups avoid it.
On the same page, “prolonged” means continuous exposure for several hours, “strenuous” means a lot of energy or effort, “reduce” means do less, “minimise” means do as little as possible, and “avoid” means do not do it.
Practical rules for a run or ride
For healthy people, short-term haze over a few days generally causes no major health issues beyond eye, nose and throat irritation. Unless the 1-hour PM2.5 reading is in Band 4 or the PSI forecast is hazardous, HealthHub says it is generally safe for healthy people to carry on with outdoor activities, at reduced intensity or duration. Drink plenty of water if you stay outdoors. N95 masks (or equivalent) are not needed for commuting between home and school or work, and they are not needed indoors.
Live 1-hour PM2.5 and PSI forecast readings are on NEA’s myENV app, the haze microsite at haze.gov.sg, and NEA’s site and social channels. Anyone who feels unwell, especially in the vulnerable groups, should seek medical attention.
