Haze health guide: what to do at each PSI and PM2.5 level
What to do at each PSI and PM2.5 level, from Singapore’s Ministry of Health: exercise, masks, vulnerable groups and outdoor work, in plain language.
MOH advice at the highest regional 24-hr PSI 222 (Very unhealthy): healthy persons: avoid prolonged or strenuous outdoor physical exertion; elderly, pregnant women and children: minimise outdoor activity; people with chronic lung or heart disease: avoid outdoor activity.
Which reading to use
Deciding now: use the 1-hr PM2.5 reading for immediate activities, such as going for an outdoor run. It reflects PM2.5 averaged over the past hour, so it shows the current air.
Planning ahead: use the 24-hr PSI and NEA’s forecast to plan tomorrow’s activities. MOH’s health advisory is built on the 24-hr PSI.
| 24-hr PSI | Healthy persons | Elderly, pregnant women, children | Chronic lung or heart disease |
|---|---|---|---|
| 0–100 Good · Moderate | Normal activities | Normal activities | Normal activities |
| 101–200 Unhealthy | 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 |
| 301+ Hazardous | Minimise outdoor activity | Avoid outdoor activity | Avoid outdoor activity |
| 1-hr PM2.5 | Everyone | Vulnerable persons |
|---|---|---|
| Band I · Normal (0–55 µg/m³) | Continue with normal activities | Continue with normal activities |
| Band II · Elevated (56–150 µg/m³) | Reduce strenuous outdoor activity for the next hour | Avoid strenuous outdoor activity for the next hour |
| Band III · High (151–250 µg/m³) | Avoid strenuous outdoor activity for the next hour | Avoid all outdoor activity for the next hour; may wear a mask to reduce exposure |
| Band IV · Very high (251+ µg/m³) | Minimise all outdoor activity for the next hour; may wear a mask to reduce exposure | Avoid all outdoor activity for the next hour; may wear a mask to reduce exposure |
Common questions
Is it safe to exercise outdoors during the haze?
Use the 1-hr PM2.5 reading for decisions in the next hour, such as going for an outdoor run. Under MOH’s personal guide, at Band I (0–55 µg/m³) everyone can continue normal activities. At Band II (56–150 µg/m³) everyone should reduce strenuous outdoor activity, and vulnerable persons should avoid it. At Band III (151–250 µg/m³) everyone should avoid strenuous outdoor activity, and vulnerable persons should avoid all outdoor activity. At Band IV (251+ µg/m³) everyone should minimise all outdoor activity. These apply to the next hour.
What should I do when the 24-hr PSI is above 100?
MOH’s health advisory is built on the 24-hr PSI and is meant for planning the day. At 101–200 (Unhealthy), healthy persons should reduce prolonged or strenuous outdoor physical exertion; the elderly, pregnant women and children should minimise it; people with chronic lung or heart disease should avoid it. At 201–300 (Very unhealthy), healthy persons should avoid prolonged or strenuous outdoor physical exertion; the elderly, pregnant women and children should minimise outdoor activity; people with chronic lung or heart disease should avoid outdoor activity. Above 300 (Hazardous), healthy persons should minimise outdoor activity and everyone else should avoid it.
Should I check the PSI or PM2.5?
Both, for different decisions. The 1-hr PM2.5 reflects PM2.5 averaged over the past hour, so it shows the current air: use it for activities in the next hour. The 24-hr PSI moves slowly and is what MOH’s advisory and NEA’s daily advice are based on: use it, with NEA’s forecast, to plan ahead.
Do I need an N95 mask during the haze?
N95 masks generally aren’t needed for short exposures like commuting. MOH advises when longer time outdoors may warrant one. Anyone with breathing difficulty should consult a doctor before using an N95.
Who is most vulnerable to haze?
MOH treats the elderly, pregnant women, children, and people with chronic lung or heart disease as vulnerable persons, and gives them stricter guidance at each level.
What should outdoor workers do during the haze?
Employers follow the Ministry of Manpower’s haze guidelines, based on NEA’s 24-hr PSI, including reducing outdoor work and providing suitable masks where it can’t be avoided.
What should I do if I feel unwell from the haze?
Seek medical advice, especially for older adults, children, and anyone with a heart or lung condition. AirAware’s guide is general information, not a diagnosis.
Sources: MOH (HealthHub: Protect yourself against haze), NEA (haze.gov.sg), Ministry of Manpower haze guidelines, US EPA (AirNow).
Source: National Environment Agency (NEA) via data.gov.sg, Singapore Open Data Licence v1.0. Health guidance: Ministry of Health (MOH) and US EPA. AirAware is not affiliated with NEA, MOH or the US EPA and does not provide medical advice. For official information, see haze.gov.sg.
Data: latest readings (JSON) · 7-day history (JSON) · llms.txt