Question 1

What PSI level is considered unhealthy in Singapore?

Accepted Answer

A 24-hour PSI above 100 is Unhealthy. NEA bands the index as 0–50 Good, 51–100 Moderate, 101–200 Unhealthy, 201–300 Very Unhealthy and above 300 Hazardous. The health advice changes at each band, and changes differently depending on whether you are a healthy adult or in a vulnerable group.

Question 2

What is the difference between the PSI and PM2.5?

Accepted Answer

The PSI is an index, not a measurement: NEA works out a sub-index for each of six pollutants (PM2.5, PM10, sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide) from their 24-hour average levels, and the highest sub-index becomes the PSI. It has no units and moves slowly. The 1-hour PM2.5 is a direct measurement of fine particles — the main ingredient of haze — in micrograms per cubic metre, averaged over the last hour, so it reacts fast. NEA says to use the 1-hour PM2.5 for immediate decisions, such as whether to go for a walk or run now, and the 24-hour PSI for planning ahead. Because one covers a day and the other an hour, they can disagree: after haze clears, the PSI can stay Unhealthy while the PM2.5 is already Normal; when haze arrives, the PM2.5 jumps hours before the PSI follows.

Question 3

Is it safe to exercise outdoors when there is haze?

Accepted Answer

NEA advises using the 1-hour PM2.5 reading, not the 24-hour PSI, for anything you are about to do in the next hour. Up to 55 µg/m³ you can continue normal activities. From 56 to 150 µg/m³ healthy people should reduce strenuous outdoor activity, and vulnerable persons should avoid it. Above 250 µg/m³ everyone should minimise or avoid outdoor activity entirely.

Question 4

Who counts as a vulnerable person?

Accepted Answer

NEA defines vulnerable persons as the elderly, pregnant women, children, and persons with chronic lung disease or heart disease. They get the stricter instruction at every level above the normal band.

Question 5

Why is the PSI different in different parts of Singapore?

Accepted Answer

Haze arrives on the wind, so the regions nearest the source read higher first. It is common for the west to be well above the east, or the reverse, depending on wind direction. This is why NEA publishes five regional readings rather than one national figure.

Question 6

Does haze affect Woodlands and Tuas checkpoint crossings?

Accepted Answer

Haze does not normally close a checkpoint or change immigration processing. What it changes is the experience of queuing: on a bad day a long wait is spent in the open air near the Causeway. Check the north reading for Woodlands and the west reading for Tuas, and the live camera feeds for how long the queue actually is.

Question 7

How often are these readings updated?

Accepted Answer

NEA publishes new readings hourly. This page reads them from data.gov.sg with a cache of at most ten minutes, so the figure shown is the most recent hourly reading NEA has released.

Hour	North	West	Central	East	South
12 am	26	32	32	30	13
1 am	27	29	32	29	26
2 am	32	33	25	32	19
3 am	37	33	27	35	34
4 am	33	37	18	32	37
5 am	38	41	18	39	35
6 am	38	40	26	35	32
7 am	38	37	29	32	33
8 am	38	34	35	35	21
9 am	44	31	39	36	40
10 am	43	47	41	36	42
11 am	43	57	46	25	34
12 pm	47	47	42	24	36
1 pm	35	39	34	19	25
2 pm	30	35	16	13	25
3 pm	11	27	11	8	13

Hour	North	West	Central	East	South
12 am	72	78	76	72	68
1 am	72	78	76	71	67
2 am	72	78	75	71	66
3 am	72	77	75	72	67
4 am	71	77	74	71	67
5 am	72	77	73	72	68
6 am	72	77	72	72	68
7 am	72	77	71	72	68
8 am	72	77	71	72	68
9 am	72	77	71	72	68
10 am	72	77	71	72	69
11 am	72	78	71	71	69
12 pm	73	78	71	71	69
1 pm	73	78	71	71	69
2 pm	73	78	71	71	70
3 pm	73	77	70	70	70

PSI	Healthy persons	Elderly, pregnant women, children	Chronic lung or heart disease
Good0–50	Normal activities	Normal activities	Normal activities
Moderate51–100Now	Normal activities	Normal activities	Normal activities
Unhealthy101–200	Reduce prolonged or strenuous outdoor physical exertion	Minimise prolonged or strenuous outdoor physical exertion	Avoid prolonged or strenuous outdoor physical exertion
Very Unhealthy201–300	Avoid prolonged or strenuous outdoor physical exertion	Minimise outdoor activity	Avoid outdoor activity
HazardousAbove 300	Minimise outdoor activity	Avoid outdoor activity	Avoid outdoor activity

Singapore PSI & haze today

Today so far

What NEA advises now

For the next hour

For the day ahead

Singapore radio · live

About these readings

Common questions