The air quality in Chiang Mai is shit today, and it's probably going to get worse.



From http://aqmthai.com/

That last indicator (PM10) shows fine particles in the air - basically soot particles upto 10 micrometres in diameter.

Thailand says the safe level is 120.

In the UK, the scale is:
low 0 - 49
moderate 50-74
high 75-99
very high >99