How to exercise your air quality sensor

Just run the mower past it :roll:


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I notice it when my neighbor fires up his BBQ. :slight_smile:

It will be interesting to see what it does during fire season.

I already saw what it was like last year right after I installed my sensor when we had those big fires north of the bay area. The smoke drifted down here and the AQI was well up over 100. But, being close to a busy intersection with a lot of cars and trucks going by, my sensor gets lots of exercise during the day with some big spikes as you can see in the graph.


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For me the graph spikes when a wood burner is started close by

There is often a correlation with humidity drops and rises - does anyone have a view on what causes this?

High humidity (fog and haze) cause higher readings for PM than the same amount of PM with a low humidity.
Those very small water-drops are measured as PM
All private stations in my area measure higher compared to the official station in the early morning when humidity is high, temp is low and wind is also at a minimum.

Official electronic PM measuring stations use the relative humidity to recalculate the real AQ or they use very small “heaters” to evaporate the water drops.

Here is my AQ page for the [color=blue][b]Luftdaten device[/b][/color] which is in-sync with the official station.
And this one for [color=blue][b]my Purpleair one[/b][/color] which is always measuring higher values.
The legenda are for Belgian/European AQ-indexes, they differ from the US ones.
Wim

Interesting, I’ll run my diesel tractor by it and see what that does.

Thanks for that info.

Or you could just wait for a big L to come roaring through as I had this past Thursday. 70+mph winds in the N part of AZ, lots of dust and sand blowing around down here. My AQI was Extreme Unhealthy and went to 1081 on the Quality Index!

Yes and no.

The “instant” AQI ( index) can be very high, but the health effects are defined for the average AQI value for 24 hours = AQHI.
So the health effects of a one hour storm is often offset by multiple hours rain, which washes away the dust.

Also a sandstorm is not measured in the AQ-indexes as the sand is far to big to have any influence on the health index.
This is an EPA picture about the relative sizes. The smallest particles are the most dangerous: PM2.5 and PM10. bigger particles are “coughed out ?” by humans.

Wim


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We have allergies. So I got myself a Winix air purifier that has an air quality sensor. what it does is speeds up the fan to clean the air. I have a couple of them, one for the dog, cuts down dander and smells, and the other that probably does the same for me.

Anyway, I got one for my daughter and took it over to her house. She decided to test it and tooted near it. Definitely it roared into action for several minutes at high fan speed and the VOC light went from blue to deep red. we had a very good laugh about it.

Thanks for that information on humidity and its effects - interesting and makes sense woodburner spikes at 180 units and you can smell the smoke but not see it!

The consistency of reading from one unit to the next in an area appears to be very good - there are now 9 units located around London