Should I trust my phone’s AQI app during Singapore haze?

Prefer haze.gov.sg and myENV for official 1-hour PM2.5 and 24-hour PSI. Foreign AQI widgets often use different sensors and scales, which is why newcomers over- or under-react.

What is the difference between 1-hour PM2.5 and 24-hour PSI?

Use 1-hour PM2.5 to decide right now (run, outdoor lunch). Use 24-hour PSI and haze forecasts to plan tomorrow’s school and training. MOH health advisories key off PSI bands because health evidence is largely built on 24-hour exposure.

When should healthy adults cut outdoor exercise in haze?

Orientation from MOH tables (verify live): reduce prolonged/strenuous outdoor exertion from Unhealthy PSI (101–200); avoid it at Very unhealthy; minimise outdoor activity when Hazardous. Children, elderly, pregnant people, and heart/lung patients tighten earlier.

Do I need N95 masks indoors during haze?

Usually no if windows are closed and a room purifier is running. N95-style masks help for longer outdoor stretches. People with heart or lung conditions should ask a doctor before prolonged masked exertion.

Is heat stress only a haze-season problem?

No. Heat stress is annual in Singapore even when the sky looks clear. Keep hydration norms for kids’ outdoor CCAs year-round; haze is an intermittent add-on, not the only climate risk.

Life

Haze, heat, and climate preparedness

1-hr PM2.5 vs 24-hr PSI, MOH health advisory bands, N95 and purifier kit, and heat-smart habits for Singapore households.

LifeLiving2 min readLast reviewed 15 September 2026

Short answer: Use haze.gov.sg / myENV, not random AQI widgets. 1-hour PM2.5 = decide now; 24-hour PSI = plan tomorrow and follow MOH bands. Stock N95s + a bedroom purifier if anyone is sensitive — and treat heat as the year-round risk, not only haze weeks.

Transboundary haze is intermittent but memorable. Heat stress is annual. Flash floods are the third climate surprise renters under-check — see flood / rental site checks. Thunderstorms and high-floor lightning anxiety are the fourth — lightning / thunderstorm living. Dengue-cluster weeks are the fifth — cluster / fogging ops. New arrivals often confuse third-party AQI apps with Singapore’s official PSI and 1-hour PM2.5 readings — then over- or under-react.

Two numbers, two jobs

Metric	Use it for	Orientation bands
1-hr PM2.5 (µg/m³)	Decide now (run, CCA, outdoor lunch)	Normal 0–55 · Elevated 56–150 · High 151–250 · Very high ≥251
24-hr PSI (and haze-season forecast)	Plan tomorrow / school and training decisions	Good 0–50 · Moderate 51–100 · Unhealthy 101–200 · Very unhealthy 201–300 · Hazardous >300

Scientific health evidence is largely built on 24-hour exposure. That is why MOH advisories key off PSI bands even when you also watch the hourly PM2.5 chart.

What to do when PSI rises

Orientation from MOH tables (verify live):

Healthy adults: reduce prolonged/strenuous outdoor exertion from Unhealthy (101–200); avoid it at Very unhealthy; minimise outdoor activity when Hazardous
Children, elderly, pregnant people: tighten earlier — minimise strenuous outdoor activity from Unhealthy
Chronic heart/lung disease: avoid strenuous outdoor exertion from Unhealthy; avoid outdoor activity at higher bands

N95-style masks help when you must be outdoors for longer stretches during haze; they are usually unnecessary indoors with windows closed and filtration running. People with heart/lung conditions should ask a doctor before prolonged masked exertion.

Household kit

Correctly sized N95-style masks for each family member
At least one decent purifier for sleeping rooms if anyone is haze-sensitive or asthmatic
Hydration norms for kids’ outdoor CCAs in heat — haze or not
myENV / haze.gov.sg bookmarked; do not rely solely on foreign AQI widgets

When PSI spikes, reschedule outdoor sport without drama. It is ordinary regional weather politics meeting biology — not a personal failure of “tropical toughness.”

Next: emergencies for 995/999 literacy, and pediatrician if kids are in the household.

Questions, answered

Should I trust my phone’s AQI app during Singapore haze?: Prefer haze.gov.sg and myENV for official 1-hour PM2.5 and 24-hour PSI. Foreign AQI widgets often use different sensors and scales, which is why newcomers over- or under-react.
What is the difference between 1-hour PM2.5 and 24-hour PSI?: Use 1-hour PM2.5 to decide right now (run, outdoor lunch). Use 24-hour PSI and haze forecasts to plan tomorrow’s school and training. MOH health advisories key off PSI bands because health evidence is largely built on 24-hour exposure.
When should healthy adults cut outdoor exercise in haze?: Orientation from MOH tables (verify live): reduce prolonged/strenuous outdoor exertion from Unhealthy PSI (101–200); avoid it at Very unhealthy; minimise outdoor activity when Hazardous. Children, elderly, pregnant people, and heart/lung patients tighten earlier.
Do I need N95 masks indoors during haze?: Usually no if windows are closed and a room purifier is running. N95-style masks help for longer outdoor stretches. People with heart or lung conditions should ask a doctor before prolonged masked exertion.
Is heat stress only a haze-season problem?: No. Heat stress is annual in Singapore even when the sky looks clear. Keep hydration norms for kids’ outdoor CCAs year-round; haze is an intermittent add-on, not the only climate risk.

Sources & citations

Admin and policy details change. Prefer the official page when making decisions; we cite primary sources for Singapore government and statutory guidance.

Two numbers, two jobs

What to do when PSI rises

Household kit

Questions, answered

Sources & citations

Related guides