The smoke is easing, but the air is not clean. A Moderate day can still hold PM10 up to 150 µg/m³ over 24 hours, which is 3.3 times WHO's 24-hour guideline of 45 (DOE Malaysia, 1997; WHO, 2021).
The monsoon removes the smoke. It does not remove the traffic, and it does not close the file on the next haze season.
The sky over the junction is blue again, and the phone says Moderate. You lift the visor an inch, because it feels over.
Singapore's 24-hour PSI read 57 to 68 across all five regions at 8 am on 31 October, the Moderate band (NEA, 2026). The question riders keep typing is whether that means the haze is gone.
The honest answer has two halves, and only one of them is good news.
Key takeaways
- A Moderate reading on Malaysia's API tops out at PM10 150 µg/m³ over 24 hours, 3.3 times WHO's 24-hour guideline of 45 µg/m³ (DOE Malaysia, 1997; WHO, 2021).
- Even outside haze, the median PM10 in 2015 was 45 µg/m³ at Muar and 47 µg/m³ at Cheras, already at or above the WHO figure (Samsuddin et al., 2018).
- Severe haze has arrived in the March to April monsoon window in 2014 and in a non-drought year, June 2013, when Singapore's PSI hit a record 246 (Nadzir et al., 2017; Gaveau et al., 2014).
- Experts expect relief from November until July, which leaves about four exposure months a year (The Star, 2026).
The research behind this
Peer-reviewed measurements this post is built on. Each card says what was measured, what was found, and what it can't tell you.
Muar and Cheras, haze vs non-haze
- What they measured
- Hourly PM10 and trace gases for all of 2015 at a semi-urban site in Muar, facing Sumatra, and an urban site in Cheras near Kuala Lumpur, with back-trajectories to trace the smoke.
- What they found
- Median PM10 was 45.0 and 47.0 µg/m³ across the year. Haze peaks reached 358 and 415 µg/m³, and PM10 and carbon monoxide ran about two times higher in haze than outside it.
- Can't tell you: two fixed stations in one El Niño year, medians not means, and not the air at rider height.
Haze in the northeast monsoon, 2014
- What they measured
- Rainwater chemistry and air-mass back-trajectories during a severe haze episode in March to April 2014, after a prolonged drought.
- What they found
- Rainwater pH fell from near neutral (6.54) to acidic (below 4.00) as haze gave way to cleaner air. Trajectories pointed to the Indo-China mainland and the South China Sea.
- Can't tell you: it is one short episode, and it measured rainwater, not what a person breathed.
The 2013 non-drought haze
- What they measured
- Satellite fire data and rainfall records for the Sumatran fires behind the June 2013 haze.
- What they found
- Singapore's 24-hour PSI reached a then-record 246 in a wetter-than-average year. The fires lasted one week and burned an estimated 163,336 hectares, 84% of it peat.
- Can't tell you: it is a single event, and the emissions estimate carries a stated uncertainty.
Population exposure, 2015 fires
- What they measured
- A high-resolution atmospheric model of the Fall 2015 fires, checked against satellite and ground observations, to estimate who breathed unhealthy air.
- What they found
- About 69 million people had persistent exposure to unhealthy air, and short-term exposure may have caused 11,880 excess deaths (range 6,153 to 17,270).
- Can't tell you: the deaths are modelled rather than counted, and 2015 was the largest fire year in two decades.
Haze and under-five deaths in Malaysia
- What they measured
- A case-crossover study of deaths in children under five across 12 Malaysian districts from 2014 to 2016, testing haze days of different intensity and length.
- What they found
- No overall association between haze and under-five mortality. A marginal signal appeared only in the districts in the low-PM category, with an odds ratio of 1.210 (95% CI 1.000 to 1.464).
- Can't tell you: it covers three years and small numbers of deaths, so a null result is not proof of safety.
What the studies actually measured
Start with the baseline, because "gone" only means something against a baseline. Samsuddin's team logged PM10 every hour through 2015 at two Malaysian sites. On the days with no haze, the median was already 45 µg/m³ at Muar and 47 µg/m³ at Cheras (Samsuddin et al., 2018).
Then the smoke arrived. The highest haze readings were 358 and 415 µg/m³, and both PM10 and carbon monoxide ran about two times higher than outside haze (Samsuddin et al., 2018).
The other studies ask when haze comes, and what it costs.
Nadzir measured a severe episode in March to April 2014, with air traced to Indo-China and the South China Sea (Nadzir et al., 2017). Gaveau reconstructed June 2013, when fires over one week in Central Sumatra pushed Singapore's PSI to a record 246 in a wet year (Gaveau et al., 2014).
Crippa and Phung look at the health side. Their results do not match, and we come back to that below.
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Moderate is not clean air, and the numbers show it
Malaysia's Air Pollutant Index was built so that API 100 equals the national guideline. For PM10, the Department of Environment's own table puts API 100 at 150 µg/m³ over 24 hours (DOE Malaysia, 1997).
WHO's 2021 guideline for the same pollutant over the same 24 hours is 45 µg/m³ (WHO, 2021). So the top of the Moderate band is 3.3 times the WHO figure.
The top of Malaysia's Moderate band for PM10 is 150 µg/m³. WHO's 24-hour guideline is 45.
Source: DOE Malaysia, 1997; WHO, 2021The bottom of the band is not clean either. The same table puts API 50 at PM10 50 µg/m³, so every Moderate day (API 51 to 100) starts above WHO's 45 (DOE Malaysia, 1997).
When the index drops to Moderate, the air is back to normal and safe to ride in.
Moderate means the air meets Malaysia's own limit. That limit is 3.3 times WHO's 24-hour PM10 figure (DOE Malaysia, 1997; WHO, 2021), and normal non-haze air in 2015 already sat near WHO's number (Samsuddin et al., 2018).
This is a limit of the index, not a failure of the agency.
The DOE guide is the 1997 edition, and current bulletins may use updated breakpoints, so check today's table before leaning on the exact figure. The shape of the argument holds either way. We unpack the wider mismatch in Same Number Different Smoke.
What is still in the air once the smoke clears
Traffic. When the smoke leaves, the exhaust is what is left, and you sit in it at handlebar height.
Carbon monoxide rose along with PM10 in the Cheras haze data, so the gas travels with the particles (Samsuddin et al., 2018). A vent does nothing about either.
Here is the engineering. A passive vent has no filter, and a 2.5 micron particle fits through any mesh a helmet could carry. At a red light there is no ram air at all, so the pocket inside the shell settles to match the plume outside.
Treat the front of a junction queue as its own exposure, whatever the app says. Drop back a few vehicle lengths from exhaust pipes while stopped.
Can the haze come back during the monsoon?
It has before. Nadzir documented a severe episode in March to April 2014, in the northeast monsoon window (Nadzir et al., 2017). Gaveau showed that a record PSI of 246 happened in June 2013, a wetter-than-average year (Gaveau et al., 2014).
Those are precedents, not a forecast. The experts quoted by The Star on 26 October expect relief from November until July, and one said next year "will not be as bad" (The Star, 2026).
A Universiti Malaysia Perlis academic put the catch plainly:
"Rainfall in our country alone is insufficient to ensure an end to transboundary haze if fires remain active at their source in Indonesia" (NST, 2026).
For the timing question itself, see our guide on when the haze ends and the restoration vs drought post.
Five more haze windows before 2031 is about 20 months
This is my own estimate, not an official forecast. A reprieve from November until July leaves roughly July to October exposed, about 4 months a year (The Star, 2026).
Five more windows, 2027 to 2031, is 4 months times 5 seasons.
That counts months when haze can arrive, not how bad it will be.
A mild year and a record year both count as one window. The long record says the bad years are real: PM2.5 deaths in Equatorial Asia roughly tripled between 1990 and 2019, concentrated in El Niño years, in a modelled estimate (Yin, 2023).
Do the health numbers agree? Not quite
Crippa modelled the 2015 fires and estimated 11,880 excess deaths from short-term exposure (Crippa et al., 2016). Phung looked at actual under-five deaths across 12 Malaysian districts in 2014 to 2016 and found no overall link to haze (Phung et al., 2022).
Both can be true. One is a model of a huge fire year across the region. The other is observed deaths in the youngest children over three varied years. The sensible reading is caution, not alarm: the signal is clear in the models and unclear in the district data.
A filter works the same on a Moderate day
Easi Breezi clips onto your helmet and passes the air you breathe through H11 HEPA media that stops at least 95% of PM2.5. It filters at your intake, so it does the same job on a Moderate day as on an Unhealthy one.
It is a particle filter. It does not remove carbon monoxide. Use the quiet months to fit it, not the week the PSI jumps. See the clip-on helmet air purifier, and for a live local check use the haze page.
Frequently asked questions
Is the haze gone?
Mostly, for now. The smoke is easing as the northeast monsoon takes over, and relief is expected from November until July (The Star, 2026). The air is not clean, because Moderate still allows PM10 of up to 150 µg/m³ (DOE Malaysia, 1997).
Is the haze over in Malaysia?
The current episode is winding down, per the experts quoted by The Star, 2026. Check your local DOE reading today before assuming it applies to your town.
Is Moderate air quality safe to ride in?
It meets the national limit, not WHO's. The top of the band is 3.3 times WHO's 24-hour PM10 figure (DOE Malaysia, 1997). Sitting in a junction queue can be worse than the station reading.
Can haze come back during the monsoon?
Yes, it has. It reached Malaysia in March to April 2014 (Nadzir et al., 2017). It is less likely in the months experts call the reprieve, but not impossible.
- Read Moderate as a ceiling, not a clean bill. It allows PM10 up to 3.3 times WHO's 24-hour figure (DOE Malaysia, 1997; WHO, 2021).
- Check your local station before each long ride. A reading from another town can mislead you.
- Stay back from exhaust pipes at junctions. Traffic is what stays when the smoke goes.
- Fit your filter now, while it is quiet. The Easi Breezi clip-on air purifier filters PM2.5 at your intake on any day.
Sources
- Department of Environment Malaysia (1997). "A Guide to Air Pollutant Index in Malaysia (API)," third edition. aqicn.org/images/aqi-scales/malaysia-api-guide.pdf
- World Health Organization (2021). "WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide." who.int
- Samsuddin, N.A.C., Khan, M.F., Maulud, K.N.A., Hamid, A.H., Munna, F.T., Rahim, M.A.A., Latif, M.T., Akhtaruzzaman, M. (2018). "Local and transboundary factors' impacts on trace gases and aerosol during haze episode in 2015 El Niño in Malaysia." Science of the Total Environment. doi.org/10.1016/j.scitotenv.2018.02.289
- Nadzir, M.S.M., Lin, C.Y., Khan, M.F., Latif, M.T., Dominick, D., Hamid, H.H.A., Mohamad, N., Maulud, K.N.A., Wahab, M.I.A., Kamaludin, N.A., Lazim, Z.M. (2017). "Characterization of rainwater chemical composition after a Southeast Asia haze event: insight of transboundary pollutant transport during the northeast monsoon." Environmental Science and Pollution Research. doi.org/10.1007/s11356-017-9131-1
- Gaveau, D.L.A., Salim, M.A., Hergoualc'h, K., Locatelli, B., Sloan, S., Wooster, M., Marlier, M.E. and colleagues (2014). "Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran fires." Scientific Reports. doi.org/10.1038/srep06112
- Crippa, P., Castruccio, S., Archer-Nicholls, S., Lebron, G.B., Kuwata, M., Thota, A., Sumin, S. and colleagues (2016). "Population exposure to hazardous air quality due to the 2015 fires in Equatorial Asia." Scientific Reports. doi.org/10.1038/srep37074
- Phung, V.L.H., Ueda, K., Sahani, M., Seposo, X.T., Wan Mahiyuddin, W.R., Honda, A., Takano, H. (2022). "Investigation of association between smoke haze and under-five mortality in Malaysia, accounting for time lag, duration and intensity." International Journal of Epidemiology. doi.org/10.1093/ije/dyab100
- Yin, S. (2023). "Effect of biomass burning on premature mortality associated with long-term exposure to PM2.5 in Equatorial Asia." Journal of Environmental Management. doi.org/10.1016/j.jenvman.2022.117154
- National Environment Agency Singapore (2026). Real-time PSI readings, 31 October 2026, 8 am. api-open.data.gov.sg
- The Star (2026). "Haze relief soon but El Nino looms," 26 October. thestar.com.my
- New Straits Times (2026). "Haze may ease by month-end as monsoon rains arrive: Academic," October. nst.com.my
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.