Singapore's PSI, Malaysia's API and Indonesia's ISPU all report haze as a 24-hour average measured at station height. A rider breathes the 1-hour peak at road level, plus the exhaust ahead, so the air at your visor is usually worse than the number on your phone.
Part of our Haze and air quality by city guide.
The number on your phone this morning was 105. On Sept 10, central Singapore's 24-hour PSI went back into the unhealthy range, as reported by The Straits Times.
It was the second crossing this episode, after a peak of 123 on Sept 4. The smoke is Sumatra and Kalimantan peat, and no index measures it at your visor.
- On Sept 4, 2026, Singapore's 24-hr PSI crossed into the unhealthy range from haze for the first time since October 2023, peaking at 123, and returned to 105 on Sept 10 (Straits Times, NEA).
- NEA's Sept 9 advisory showed a 24-hr PSI of 74 to 98 ("Moderate") while the 1-hr PM2.5 concentration ran 43 to 85 µg/m³, a live example of the gap between the headline index and the street.
- Malaysia's Ministry of Health reported asthma presentations up 259% in the last week of August 2026 while the Sarawak haze emergency was declared and then cancelled with air still "very unhealthy" (ABC News).
- Regional unhealthy-range haze episodes have recurred on a 3 to 4 year El Niño-linked cadence: 2015, 2019, 2023, 2026. If the cadence holds, at least one more multi-week episode arrives before 2031.
This is the fourth episode since 2015
Unhealthy-range haze returns every 3 to 4 years, in step with El Niño: 2015, 2019, 2023 and now 2026. This year a super El Niño is behind it, and Indonesian officials told ABC News on Sept 7 that conditions are worse than in 2015, the benchmark crisis year.
Malaysia declared a haze emergency in Sarawak when the API crossed the 500 trigger, then cancelled it days later while the air stayed "very unhealthy". The smoke doesn't read policy lines.
Malaysia's Ministry of Health recorded the jump in asthma presentations in the last week of August 2026.
Source: Malaysia Ministry of Health, via ABC NewsMetro Manila, a fourth capital, logged "acutely unhealthy" air from Aug 30 to Sept 2.
You breathe the peak, and the index reports the average
NEA's own Sept 9 haze update showed the gap.
Against a WHO 24-hour guideline of 15 µg/m³, a peak-hour rider takes their dose from the top of that 1-hour band. The index then averages it away against clean overnight hours.
Two more things add to it:
- Height. Index stations sample well above the road. Your intake sits at about tailpipe height, in the freshest part of the plume. More in why air quality apps mislead riders.
- Exhaust adds to the haze. Idling, you breathe peat smoke plus the exhaust ahead. No national index models the sum.
On a haze day, don't sit right behind a tailpipe at the lights. That is where exhaust piles onto the smoke. Live haze readings
What the index says vs what you breathe
Here is what the index reports, next to what a rider on the same street takes in.
| What the index says | What a rider breathes |
|---|---|
| A 24-hour average | The 1-hour peak. On Sept 9 the PSI read 74 to 98, "Moderate", while 1-hour PM2.5 ran 43 to 85 µg/m³ (NEA). |
| Air sampled well above the road | Air at about tailpipe height, in the freshest part of the plume. |
| Regional haze | Haze plus the exhaust of the vehicle ahead, stacked at the lights. |
| A number that includes clean overnight hours | A dose taken at 8 am in stopped traffic, against a WHO 24-hour guideline of 15 µg/m³. |
You cannot make the index read the road. You can decide what air reaches your lungs on the ride.
Ride with filtered air
Filters haze PM2.5 on every ride
Easi Breezi mounts on your scooter or motorbike and feeds H11 HEPA-filtered air into your helmet. Bike-powered, no batteries, no charging.
PSI, API and ISPU are all built the same way
Each one rolls readings from fixed monitoring stations into one number and headlines a 24-hour average.
| Index | Country | Published by |
|---|---|---|
| PSI | Singapore | NEA |
| API | Malaysia | Department of Environment (APIMS) |
| ISPU | Indonesia | Ministry of Environment and Forestry |
The scales differ a little at the top. That's why the same smoke read 105 in Singapore, "very unhealthy" in Malaysia, and off the chart in Pontianak, where ABC News reported AQI readings above 900 on Sept 7.
For a rider, the shared design matters more than the labels. It's a public health planning tool, never meant to describe what you breathe at 8 am in stopped traffic.
Expect at least one more episode before 2031
This is our own projection from the interval pattern and a worsening severity trend, not a forecast of concentrations. If the rhythm holds, riders in Indonesia, Malaysia and Singapore face at least one more multi-week episode before 2031.
The official advice never changes: stay indoors, wear a mask. For the tens of millions who commute by motorcycle, staying indoors isn't an option.
City guides for riders: Singapore, Kuala Lumpur, Medan.
The gap is one you can close
You cannot move the monitoring stations or bring the rain forward. The part of the dose you control is the air at your own intake.
The 1-hour PM2.5 reading is already published in NEA's updates, and it sits closer to what you breathe than the 24-hour PSI. Time spent idling behind a tailpipe is the next biggest piece, and it is yours to cut.
Filtering at the helmet covers the rest, and it keeps working in stopped traffic, where exhaust on haze is worst.
Filter the air where you breathe it
No national index measures your own intake, so that's where to filter. Peat smoke PM2.5 is mostly submicron, close to the size that slips through filters most easily.
| Option | Stops submicron smoke? | Why |
|---|---|---|
| Open visor | No | Passes it straight through |
| Passive helmet vents | No | Pass it straight through |
| Cloth mask | No | Not a filter for particles this small |
| Active HEPA-filtered airflow | Yes | Pushes filtered air in, even at idle |
An active system like the Easi Breezi unit needs no forward motion, so it keeps working at idle, where exhaust on haze is worst. Smoke loads filters faster, so keep spare HEPA filters on hand.
Don't want to keep checking?
Frequently asked questions
What does a PSI of 105 mean for riding a motorcycle?
It's in Singapore's unhealthy band, and the street-level PM2.5 you breathe while riding is usually higher. Ride less, avoid idling behind vehicles, and filter at the helmet instead of relying on a closed visor.
Is PSI the same as AQI?
No. PSI, API, ISPU and the US-style AQI in many apps use different formulas and breakpoints, so one plume gives different numbers. All headline a 24-hour average.
Is it safe to ride a motorcycle in haze?
Your PM2.5 dose runs well above the index, because you breathe road-level peaks plus exhaust. If you must ride, cut time in stopped traffic and use HEPA-grade filtration, since cloth masks and vents don't stop submicron smoke.
Will the haze come back after 2026?
Probably. If the 3 to 4 year pattern holds, at least one more multi-week episode before 2031 is the base case.
What to do before the next haze day
- Check the 1-hour PM2.5, not only the 24-hour PSI. It's closer to what you breathe.
- Cut your time in stopped traffic, and don't idle right behind a tailpipe when you can avoid it.
- Filter at your intake, not with a cloth mask or open vents.
The index will tell you about the next episode a day late and an average short. Filter at your own intake instead.
Written by Ash, mechanical engineer and founder of Easi Breezi, building an active HEPA filtration system for motorcycle helmets (patent pending). Based between Hong Kong and Bali, riding daily in the traffic this blog writes about.