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Comment by Scene_Cast2 | Hacker News Reader

How do you all monitor air quality?

I personally have a couple of devices (an Awair and a Flow). They seem to under-report PM2.5 compared to purpleair, airnow, and waqi.

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The South Coast (California) Air Quality Management District does some really thorough tests on the quality of the various low-cost sensors: https://www.aqmd.gov/aq-spec/evaluations/summary-pm

Anyone want to review this table and suggest a currently commercially available option in the $300 and lower price range? I may have time this afternoon but if anyone does go thorough it I'm interested to know.

Based on my reading of the table, the PurpleAir II sensors seemed to be the best of the sub $300 for PM1.0 (field R^2 of 0.96 to 0.98) and PM2.5 (field R^2 of 0.93 to 0.97). The PM10 readings were not as good (field R^2 of 0.66 to 0.70).

After skimming the rest of the table, it looks like the PurpleAir II sensors might have some of the best field R^2 for PM 2.5 and PM 1.0

I agree, looking at devices around the sub-$300 price point that were lab tested, PA-II has good performance and seems to be readily available.

That sensor is also available from Adafruit: https://www.adafruit.com/product/3686 I got it hooked up to a RaspberryPi that exposes sensor readings in Prometheus format.

Do you have a PurpleAir II to compare against? I suspect that there will be some extra calibration or signal processing some to make it more accurate that will be missing in the raw sensor.

EDIT: The link we're discussing says this explicitly: "[...] These particle counts are processed by the sensor using a complex algorithm to calculate the PM1.0, PM2.5 & PM10 mass in ug/m3. [...] PurpleAir PA-II uses two identical PMS5003 sensor units attached to each other and placed in the same shelter. [...]"

I don't think you can recommend the PMS5003 as a substitute for the PurpleAir II.

That sensor available at Adafruit uses the same algorithm for calculating PM levels, it's literally the same chip. Maybe using 2 of them yields more accurate results though.

The specs for particulate matter are identical:

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

https://cdn-shop.adafruit.com/product-files/3686/plantower-p...

The Adafruit sensor is just the sensor, the PurpleAir II is two sensors plus extra logic that processes the readings to give extra accuracy.

You can't expect one sensor to give the same performance as two sensors plus correction logic. If it was that easy, PurpleAir could just put a case on a PMS sensor and be done with it.

If that was true, then why are the specs for the PurpleAir II identical with the Adafruit sensor ?

You provide absolutely no data to back up your claims that there is extra logic on the PAII or that 2 sensors are better than one.

>*Field R2

Under the table is definition of R^2

>The coefficient of determination (R2) is a statistical parameter measuring the degree of relation between two variables. ....

The more - the better. Range [0; 1)

More device in your area === better quality of measurement

Isn't the table sorted alphabetically?

True

My bad

I like the IQ air sensors https://www.iqair.com/us/air-quality-monitors/airvisual-pro

I have one of these and it's easy to hook it into your home automation stuff as it presents a CIFS share and it's simply a matter of attaching and reading a text file.

However, the damn thing turns on it's front display and backlight randomly at all hours of the day and night. If you are a sensitive sleeper this thing definitely can't be on your list of items. I contacted their support and was ignored. Generally wouldn't recommend.

you can try changing the power saving mode (under 'performance'). it lets you adjust when the screen auto turns off/on

If you just want a sensor rather than a full retail device I'd recommend the SPS30. I have one and it's very easy to work with and per that table, is very accurate, while not needing any extra software correction. It's also cheaper than that table suggests: you can buy it for ~$50USD from Mouser.

Measurements from PurpleAir's network of public sensors are available for free.

It's a useful tool if the locals in the area that you're interested in are using PurpleAir's sensors.

https://www.purpleair.com/map?opt=1/mAQI/a10/cC0#1/25/-30

The inexpensive SDS011 holds up very well and works for this global citizen science project very well: https://luftdaten.info/evaluation/

I have a uHoo monitor (yes, it is a dumb name).

https://uhooair.com/

It logs temperature, relative humidity, air pressure, CO2, CO, TVOC, PM2.5, NO2, and ozone. They are about $300. The device itself doesn't have any UI; you need to connect to it via a phone app.

Do you act on this information? Is there really much you can do to mitigate the effects?

> Do you act on this information? Is there really much you can do to mitigate the effects?

Couldn't you run a HEPA filter to reduce the particulates?

https://phys.org/news/2018-09-indoor-hepa-filters-significan...

If you have central air, you can put a good filter in your air return. If you don’t, you can buy a standalone air purifier.

Personally I have a PurpleAir II filter (as mentioned in a different part of this thread.) I also turn wood in an indoor environment, and run a HEPA filter which reduces the PM2.5 in the air drastically, and quickly.

For me just running an evaporative cooler roughly halves the counts, but that's from over 100 to about 50 so it's a kinda of a mixed blessing. But since my rented house isn't airtight or even close to it, there's not a lot I can do other than move.

I've built my own "IoT" Sensors by hooking up a bunch of components to an ESP32 on a breadboard. I ended up going with:

- CO2: Sensirion SCD30

- Particulates: Amphenol SM-UART-04L

- VOC: Sensirion SGP30

- Temperature/humidity/pressure: Bosch BME680

After hooking everything up I just wrote some code to pipe sensor readings to InfluxDB, which is connected to Grafana.

In the end I have no way of properly testing accuracy but the sensors are consistent between units and behave as expected when exposed to fresh air, which is the most I can look at right now.

Any idea how good the Awair monitors are? I recall a report saying they were just so-so but Awair recently updated them to be more accurate.

I personally use an IQAir Air Visual which is highly rated and meant to be very accurate as far as consumer grade stuff goes. It's solid, reliable and the iOS app has been great.

That said after installing piHole I noticed it making 17000 DNS requests a day to a non-existent host: https://imgur.com/tPgwGoK

Explains why the DNS Resolver on my router (pfSense) kept crashing at least.

I have pms3003 you can get for about 12 USD on AliExpress.

I bought a small usb-to-serial adapter connected to Raspberry Pi Zero W.

Here's a combo with a similar device here:

https://www.aliexpress.com/item/32617788139.html?spm=2114.12...

There are plenty of comparisons available online, but there's a good overview site here: https://aqicn.org/sensor/

I have an Awair and two Foobots, they're basically completely unreliable and the software for them is pretty bad.

I've been tempted to get the purple sensors because at least the purple map seems reliable (so maybe their stuff is better?).

I have an Awair. I don't really trust the baseline values but I do trust the deltas. I mostly use it to inform me when I should open a window or turn the air purifier or humidifier on.

I have an arduino uno hooked up to CCS811 (a tiny air sensor chip). We're floating around 550ppm C02 right now, but earlier I was terrified as I watched the levels spike to 4500.

I have Xiaomi Mijia Air Detector and Xiaomi Mi Purifier 2S. The air detector reports CO2, PM2.5 and TVOC, Purifier reports only PM2.5.

Dylos AQM is the gold standard. It's pricey though and has an old school interface (no fancy UI, IoT or "AI").

I have a uHoo and it’s been great. The readings are inline with some control sensors I got to test the readings.

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