This wildfire season, I got myself an outdoor air quality sensor. For smoke wafting from 100s of km away, the most interesting metric is PM2.5 (particulate matter under 2.5 micrometers in diameter).
As you'd expect, when the air is blue, and everyone's coughing and their eyes are burning, the reported PM2.5 is pretty high (100+ µg/m3). And when the PM2.5 is down to 3 or 4 µg/m3, the air is very clear.
But then one's expectations fall apart. Humidity doesn't actually improve the air quality--it just ameliorates the worst of the symptoms. Rain generally doesn't settle the particulate matter out of the air. And, horrifyingly, there's a wide range of unhealthy values that are not detectable to humans.
The WHO's guidelines are that the concentration should not exceed 5 on a yearly average, and shouldn't exceed a daily average of 15 for more than a few days a year.
Outside, right now, the air seems fresh and clear....and the sensor is reporting 29 µg/m3. The air I breathe is shortening my life, and I can't do a damn thing about it.
As you'd expect, when the air is blue, and everyone's coughing and their eyes are burning, the reported PM2.5 is pretty high (100+ µg/m3). And when the PM2.5 is down to 3 or 4 µg/m3, the air is very clear.
But then one's expectations fall apart. Humidity doesn't actually improve the air quality--it just ameliorates the worst of the symptoms. Rain generally doesn't settle the particulate matter out of the air. And, horrifyingly, there's a wide range of unhealthy values that are not detectable to humans.
The WHO's guidelines are that the concentration should not exceed 5 on a yearly average, and shouldn't exceed a daily average of 15 for more than a few days a year.
Outside, right now, the air seems fresh and clear....and the sensor is reporting 29 µg/m3. The air I breathe is shortening my life, and I can't do a damn thing about it.