Author Topic: Everything you ever wanted to know about air quality devices - sort of!  (Read 48 times)

elagache

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Dear WeatherCat faithful,

For the third year in a row, our household has been seriously disrupted by pollution from wild fires.  That was motivation enough to look into buying one of the air quality devices that are commonly mentioned in weather and air pollution related websites.  My attempt to find information on this turned out to be much more difficult than I imagined.  For example, I hoped that Consumer Reports might have some reviews on air quality measuring devices, but they haven't come that far.  Some cautious web searches were also in vain.  With the obvious resources not panning out, I turned to one of the premier sources of information on this sort of thing: WXForum

Here I found much more useful information.  For example, I found this review of 4 air quality sensor devices:

https://www.wxforum.net/index.php?topic=38495.0

2 of the 4 only work with weather stations of the same manufacturer, so it turns out there are relatively few choices out there.  Indeed the #1 player is PurpleAir:

https://www2.purpleair.com/collections/air-quality-sensors

Still, WXForum offered a whole lot more information about these devices than first meets the eye.  For starters there is a project to clone the PurpleAir device:

https://www.wxforum.net/index.php?topic=33857.0

It turns out what are called "air quality sensors" are in fact examples of the Internet of things.  Moreover, they aren't being created by their manufacturers.  Instead, they are assembled using components that can be easily purchased - thus making a clone possible.

Davis Instruments just launched their own air quality sensor - AirLink:

https://www.davisinstruments.com/airlink/

The PurpleAir and Davis devices work in basically the same way.  There is a sensor from a 3rd party manufacturer.  This sensor is queried by an embedded processor (aka computer) and it performs all needed calculations and other processing.  Also connected to the device is a WiFi platform that allows this tiny Internet of things device to get out on your home area network.

Not surprisingly, WXForum had a lengthy conversation about the Davis AirLink when it was announced:

https://www.wxforum.net/index.php?topic=40268.0

Among other things, the weather geeks over there concluded that is operates just like the PurpleAir device, but uses a sensor from another manufacturer.  In both cases these sensor devices only measure one kind of pollution: particulate pollution.  This is done by using laser light to reflect off the particles and from this process determine the size and quality of particles in the air.  That happens to be just the pollution associated mostly with wild fires, but is by no means the only source of air pollution.  For a quick education on the matter you can consult the Wikipedia article on air pollution:

https://www.wikipedia.org/wiki/Air_pollution

Still, anyone considering one of these air quality sensor devices might be considered of measuring only one sort of pollution.  PurpleAir is already on the case and working on a new version of their devices that would also measure volatile organic compounds.  Once more the geeks at WXForum on the bleeding edge and have adapted a PurpleAir device with the new sensor:

https://www.wxforum.net/index.php?topic=39563.0

Still that only covers 2 of the possible pollutants.  The EPA AirNow websites mention ozone as yet another important pollutant, and I couldn't find any hobbyist sensor device that could measure that.

There is one more issue that should be near and dear to all WeatherCat users.  An air quality sensor device isn't very interesting unless there is some hope that our fearless leader Stu, might be able to eventually "uncan" the device to get access to the data.  While it is possible to get access to the PurpleAir device data, it appears to be impossible to query the device directly.  The data is only available on the PurpleAir website.  While one would hope for better, it is clear that in the cut throat world of cloud computing, companies have held user's data effectively "hostage."  The worst example, I'm aware of is the photobucket policy change that forced users who had their images displayed on user forums for free, to pay for he privilege.

According to Mark Crossley, the Davis AirLink does have a device API which means WeatherCat could get the air quality data directly on your home network.  That's in my mind a plus.

After going through all this research, I'm left with something of cold feet with respect to buying one of these devices.  It seems to me that this is a very dynamic area and that better products could show up rapidly.  Still, the deciding factor for me will most likely be how the California wild fire season unfolds.  If particulate pollution continues to be a major issue for our household - I might reconsider.

I called this thread:  "Everything you ever wanted to know about air quality devices - sort of!" with good reason!   I hope that it has answered at least some of your questions.  However, should it include any serious errors or omissions, by all means please do correct them on this thread!

Cheers, Edouard  [cheers1]

Blicj11

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Re: Everything you ever wanted to know about air quality devices - sort of!
« Reply #1 on: September 12, 2020, 10:43:21 pm »
Thanks for this thorough and helpful summary of what we need to know. Nice work and much appreciated. I'm also in a wait and see mode.
Blick