The numbers numbers don't lie of course but it's interesting how perception and subjectivity play such a large role in all of this. 2015 was the first year I ever had to buy a mask, driving from Chiang Mai to Chiang Rai we stopped at a 7/11 to buy them because the pollution was so pervasive - but here in leafy Mae Rim this year it could even be that the numbers are worse now than then, but we'd never realize it because there's hardly any visual indicators, just plenty of trees. And 2007: we escaped to Phuket as I recall hence we missed the worst of it.

To Chiang Mai bro, yes it sometime can get subjective.

In 2015, Chiang Rai stations recorded values of over 500ug/m3 PM10. You could have driven through levels higher than that if you were closer to the vicinity of some hotspots ie high background levels + local fires on top of that. Entirely possible.

For gear heads, what you can get is those nifty laser particle counters outputting in ug/m3 and also particle counts. On china website taobao, they go for approx 40-50usd. It's very very sensitive, and it ought to be somewhat accurate in N thailand where RH levels are not high. (It get skewed a bit by higher levels of humidity)

Edit - the calculation of the PM needs a RH% of 35% for the sampled airflow. That's the scientific standard. Chiang Mai's RH is excellent for that actually.

Up up and away. 486ug/m3 1200h for 73t Chiang Rai!

Sawasdee Khrup,

Many thanks for the reporting, and information, by those of you active on this thread !

I was looking at the PM 2.5 values for April 3,4, and thinking about what time of day/night a bicycle ride would encounter less toxic air. Seems like the 3rd. shows a spike in the early AM hours, the 4th. a spike at 11AM. I am a manoot kan khaew (literally: bat-man; maps to English idiom: 'night-owl'), anyhow

Of course, I would rather ride my bike at night when it's cooler, and less traffic, and the injury from being blind-sided by another drunk/stoned/texting motorized-wheeled-killing-machine so-called driver is more likely to be quickly fatal; methinks a lingering death in the icu would probably exhaust my funds for a bang-up cremation, and wake. And, the early AM rides have the extra adrenaline stimulating properties of random encounter with feral demonic entities posing as farang-flesh-hungry canines.

cheers, ~o:37;

Orang37, wear a N95 nask if you must. It's going to be uncomfortable during cycling but it's for the sake of your health.

Levels of 80-120 ug/m3 PM2.5 is not sky-high but neither is it healthy considering that you are breathing some 8-10X that of normal if you are going to cycle fast.

Orang37:

The last time a similar question was asked, the answer came back that the optimal time to avoid polluted air from burning was between 2pm and 4pm, the rationale for this was:

the majority of burning is usually done in the evening with some done early morning hence by mid afternoon the majority of the smoke has cleared.

by that time of day the air has been sufficiently heated to overcome the effects of the inversion layer and trapped pollution has been released.

Separately:

Looking at the fire maps this morning I see very very few fires in Thailand, is the extreme heat keeping burners inside perhaps?

CM getting smoked quite a bit today.

Drove up to Nan yesterday. Just awful and worse today. Many fires along the roads and out in the forest. Not agricultural burning but maybe cigarettes tossed out into the dry tinder everywhere.

Drove up to Nan yesterday. Just awful and worse today. Many fires along the roads and out in the forest. Not agricultural burning but maybe cigarettes tossed out into the dry tinder everywhere.

What you saw is burning, often it's army or municipal workers burning back roadside growth to keep it under control.

Yeah, some are controlled burning....to keep a bigger fire under control. Fire breaks/fire lines.

They do that elsewhere too like in Australia, western countries.

Drove up to Nan yesterday. Just awful and worse today. Many fires along the roads and out in the forest. Not agricultural burning but maybe cigarettes tossed out into the dry tinder everywhere.

What you saw is burning, often it's army or municipal workers burning back roadside growth to keep it under control.

Yeah and it just adds to the smoke haze when they could use brush cutters.Did 1,400 kms recently, roadsides burning kms from anywhere,senseless.

Drove up to Nan yesterday. Just awful and worse today. Many fires along the roads and out in the forest. Not agricultural burning but maybe cigarettes tossed out into the dry tinder everywhere.

What you saw is burning, often it's army or municipal workers burning back roadside growth to keep it under control.

Yeah and it just adds to the smoke haze when they could use brush cutters.Did 1,400 kms recently, roadsides burning kms from anywhere,senseless.

Understand that brush cutters require capital expense to buy the machines, fuel to drive them and people to operate them, several needed to cover a fairly small area. I litre of petrol and a box of matches wins in the cost comparison stakes. Am not supportive or advocating burning, just trying to explain that it's not senseless in everyone's eyes.

Huai Kon, Chaloem Phra Kiat, Nan

The fire map is working again with hourly updates - who is taking bets that this will be the longest season we had? No rain and they will burn until 2017

http://www.ehabich.info/images/synchro/asia.jpg

Can we just cut and paste the 2015 discussion on the smog into the 2016 discussion? Nothing much has really changed.

What happened to station 36t ?

36t Si Phum, Mueang, Chiang Mai

Huai Kon, Chaloem Phra Kiat, Nan

If only I could work out how to find this graph - apparently showing both PM2.5 & PM10 right up to date. But I've tried several times and failed

Not looking Good Today

After the Wind and Dust

"Baby, the rain must fall..." Soon, I hope!

Or, to be modestly analytical, it is truly scary how much more a percentage PM<2.5 is of PM<10 is than previous research available to us appears to be, at least locally. In local research (Northern Thailand), as much as I can find, it was shown that the generally accepted 40 - 60% range for burnng rice straw was low. Now, what with corn production, my understanding is that there is a more serious problem!

"Baby, the rain must fall..." Soon, I hope!

It did, today, darling!

What happened to station 36t ?

36t Si Phum, Mueang, Chiang Mai

At that time there was a very sudden and heavy wind in the area and a lot of dust was blown around. Lasted about 15 minutes, and the monitoring station picked that up I'm guessing. Was followed by a bit of rain which presumably cleaned things up again a little bit, though the rain was unfortuntely short-lived.

What happened to station 36t ?

36t Si Phum, Mueang, Chiang Mai

At that time there was a very sudden and heavy wind in the area and a lot of dust was blown around. Lasted about 15 minutes, and the monitoring station picked that up I'm guessing. Was followed by a bit of rain which presumably cleaned things up again a little bit, though the rain was unfortuntely short-lived.

I see, that figures. Coz the PM2.5 was pretty low.

I don't know about you guys but after looking for several weeks to the incredible low readings on air4thai app I deleted it this morning don't need to look at fairy tales figures everyday.

I lived in HKG for a while and when the air looked like this the readings were much higher. Are the machines broken? Or possibly not being read correctly?

A cynical type might suspect some TAT involvement - especially since CM wants as many tourists as possible for Songkran.

I'm quite certain no none would lie to us!

Perhaps the app is correct. Usually the AQI itself, and the various factors that make up parts of it (pm10/pm2.5, CO, NO2, etc.) are calculated based on the average of the last X hours I believe.

See e.g. "https://www.airnow.gov/index.cfm?action=resources.conc_aqi_calc". Some of the factors are based on a 24 hour average, and it looks like that is what the air4thai app uses. E.g., at the moment, the last pm10 reading from the aqmthai site is 82, while air4thai says 114, which is pretty close to the 24 hour average reported at 118 by aqmthai. The air4thai app appears to be able to get slightly more recent data than the data published by aqmthai (air4thai says it got data at 11:00, but aqmthai has at the moment only published data up to 10:00).

What I think is not correct is the smiling icon for an AQI of 96. The AQI of 96 may very well be correct, but that is not something to "smile" about. Looking at "https://airnow.gov/index.cfm?action=aqibasics.aqi" again, an AQI of 96 is "moderate", and very close to "unhealthy for sensitive groups" (AQI 100 and up).

Since the aqmthai.com website says the AQI should "not exceed 100", perhaps that is why the app is showing a smiling face at an AQI of 96. I don't think there is any reason to suspect the app, or aqmthai.com, is lying about the numbers. As long as the numbers it displays are correct, which they appear to be, one can simply chose to apply the international ratings instead, which is that an AQI of 96 is borderline unhealthy, and that a pm10 24 average reading of 114 is far above the 50 ug/m3 used as max other places (e.g, in the EU).

Myself I find it much more useful to look at the hourly readings at aqmthai.com website. That is what I use when I consider whether I should do some hard interval training outside as planned, or whether it is better to lift some weights inside. E.g., a pm2.5 reading of 100 the last hour? I'll stay inside, thank you very much.

The water control folks have flooded the klongs in my neck of the woods, not just one but all of them and very heavily also! Hard to believe that's a show of support for Songkran and to keep the people happy, especially since poster Mosha in a separate thread reports winds now coming from the Adnaman side. The Westerly monsoon is in sight, the bad air is about to begone, you heard it here first!