Author Topic: Purpleair Range  (Read 387 times)

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Offline azchrisf

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Purpleair Range
« on: February 01, 2018, 09:36:15 AM »
Does anyone know or have a guess as to how big of a circumfrence this sensors measurement would be valid for?
I'm assuming the results are good for at least 1/2 mile.

IIRC the AirNow stations does miles in each direction.

Offline Toxic

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Re: Purpleair Range
« Reply #1 on: February 01, 2018, 12:27:54 PM »
not sure you can really range the sensor, but some more pdf's here:

http://www.aqmd.gov/aq-spec/product/purpleair-pa-ii

Regards Simon


Offline Eno

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Re: Purpleair Range
« Reply #2 on: February 11, 2018, 11:14:55 AM »
Depends on what kind of site the sensor is located in.  High density urban?  Heavy industrial?  Rural, open country?

Probably either what EPA terms "Middle Scale", where sensors would show show significant differences between locations that are ~0.1 to 0.5 km apart, or I'm guessing more common would be "Neighborhood Scale" 500 m to 4 km.


Offline azchrisf

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Re: Purpleair Range
« Reply #3 on: February 11, 2018, 11:39:14 AM »
Suburban.

Offline Forever

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Re: Purpleair Range
« Reply #4 on: February 11, 2018, 12:08:10 PM »
Like with our weather stations it is only really accurate for the location it's installed.

You may have a source of pollutant that my not exist only a few hundred feed away or vice versa.

Looking at the PurpleAir map I tend to have readings close to the sensors around me but as the distance grows so can the difference in the readings.
« Last Edit: February 11, 2018, 12:19:27 PM by Forever »

Offline Eno

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Re: Purpleair Range
« Reply #5 on: February 11, 2018, 12:37:48 PM »
It's a sample point; n = 1.  The more sample points the better to estimate a true average.  I think that's the advantage of the PurpleAir network, because it is better at showing the spatial variability of PM concentrations.  The EPA monitors are supposed to represent air quality for large populations of people, but the nearest one to me is 7 miles away and I noticed, way back when my PA sensor was online  :sad:, that the EPA monitor didn't always represent the air quality around my neighborhood.

Some details about air quality monitor network design:

https://www3.epa.gov/ttn/amtic/files/ambient/pm25/network/r-99-022.pdf

Offline azchrisf

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Re: Purpleair Range
« Reply #6 on: February 11, 2018, 12:44:58 PM »
Well, hmm...I've marked my sensor as being semi-accurate for about 1/2 mile around me for my neighborhood.
*Technically* that may not be correct, but I think it gives a pretty good indicator of the overall pollution level in the neighborhood.

Offline Eno

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Re: Purpleair Range
« Reply #7 on: February 11, 2018, 01:09:28 PM »
Well, hmm...I've marked my sensor as being semi-accurate for about 1/2 mile around me for my neighborhood.
*Technically* that may not be correct, but I think it gives a pretty good indicator of the overall pollution level in the neighborhood.

It looks pretty homogeneous from the imagery. Seven other sensors in Phx and at the moment they're all showing 1 or 2!  Probably more variability on bad air days?  Valley Surface of the Sun. I used to live in Globe; would've been interesting to have a PA sensor there, downwind from the copper smelter.

The PA map shows 2 sensors at your house. :?:

Offline azchrisf

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Re: Purpleair Range
« Reply #8 on: February 11, 2018, 01:12:51 PM »
Well, hmm...I've marked my sensor as being semi-accurate for about 1/2 mile around me for my neighborhood.
*Technically* that may not be correct, but I think it gives a pretty good indicator of the overall pollution level in the neighborhood.

It looks pretty homogeneous from the imagery. Seven other sensors in Phx and at the moment they're all showing 1 or 2!  Probably more variability on bad air days?  Valley Surface of the Sun. I used to live in Globe; would've been interesting to have a PA sensor there, downwind from the copper smelter.

The PA map shows 2 sensors at your house. :?:
Oh yes it's variable on other days, a big bought of wind came through over night and cleared out the air. The other one is inside, I need to have them remove it from the map.

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