Thread by @jeffgilchrist

Outdoor Particulate Matter (#PM) Air Quality Monitoring

This thread explores the new Model X #outdoor PM air quality monitor made by #Canadian @IndianaTux at , what it does, costs, and examples showing the information it provides. #AQ #AirQuality 🧵1/ co2.click

An unrolled one-page web view for this long thread that may be easier to read or share can be found here ( ). 2/

https://twitter.com/jeffgilchrist/status/1741241680752206277

After all the major wildfire smoke events this past summer, I wanted to get an air quality monitor that was suitable for outdoors so I would be better informed what the PM levels were in my neighbourhood. 3/

The closest government PM monitoring station is about 20 km away in the downtown core and frequently does not reflect the same PM levels in my part of town. 4/

A common outdoor PM monitor is the PurpleAir but is very expensive and has import duty/taxes for people in Canada. Instead, I decided to purchase a Model X for about half the cost. More details on costs later in the thread. 5/co2.click

The Model X has a high quality Sensirion SPS30 PM sensor ( ) which uses laser scattering for precise measurements. This sensor provides actual measurements for PM1.0 and PM2.5 sizes, and extrapolates the values for PM4.0 and PM10 sizes. 6/sensirion.com/products/catal…

Model X also measures barometric pressure, temperature, and relative humidity with a Bosch BME280 sensor ( ). 7/bosch-sensortec.com/products/envir…

One of the more unique features of the Model X is that it provides free long-term data collection and storage in their cloud portal for 48 months which you can view via web browser or download the data in CSV format to keep indefinitely. 8/

You connect the Model X via WiFi to an Internet connection and it will collect data every minute and send it to the portal. 9/

The online connection also allows the device to download firmware updates with bug fixes and new features over time, and Model X supports the MQTT IoT messaging protocol ( ). 10/mqtt.org

Since the Model X was designed for outdoor use, you can see the components are encased in a weather proof container and powered by a USB-C cable. I placed mine on our porch away from any exhaust vents which also allowed me to plug the Model X into our external outlet there. 11/

It is also possible to purchase a solar panel and battery kit to mount it more remotely away from electrical sockets. 12/

The portal is what really makes the Model X stand out with easy to access information and graphs. The main dashboard when you log in shows the latest reading of temperature, humidity, barometric pressure, and PM 1.0, 2.5, 4.0, and 10 levels. 13/ co2.click

Particulate matter (PM) floats in the air in different sizes such as PM2.5 particles < 2.5 micrometres (um) from combustion, organic compounds, and metals and cause serious health problems ( ). 14/ epa.gov/pm-pollution/p…

Clicking on the "Graph" button allows you to view the data over various time frames including the last 1h, 5h, 12h, 24h, 48h, and 7 days. You can also configure the default time period for graphs depending on your preference. 15/

With "Last 7d" selected, you can see the low pressure system that came in with the readings on the top left of the graph, all the changes in humidity throughout the week in the middle, and the temperature fluctuations during the day and night at the bottom. 16/

If you want to hide one or more of the readings, you can click on the legend to remove that item from the graph. 17/

Clicking on the "Particulate Matter" tab brings you to a second graph, showing you all the PM readings, in this case over the last 48 hours. We were experiencing some kind of PM event in the city over a couple of days with levels rising to 30 ug/m3. 18/

If you want to save a copy of the graph, click on the blue button in the bottom right corner with the arrow pointing down, this will download an image of the graph for you to keep and use. 19/

Having long-term air quality data stored lets you do some interesting analysis after the fact. While I was hoping our AQ troubles were over when summer finished, the city has had multiple high PM events over the past couple of months. 20/

There was one strange PM event in the middle of the night on Dec. 18, 2023 starting around 1:30am. PM levels instantly spiked to almost 60 ug/m3 then dropped to about 25 ug/m3 and then back to normal, only to spike to above 30 ug/m3 again just before 5am. 21/

Sometimes you can have very local and temporary PM increases such as while you are mowing your lawn, but checking other PM sensors in the city, I was able to find the same shape and duration of PM spike in purple air sensors 5km away (8.5 ug/m3), 17km away (16 ug/m3). 22/

I'm not sure what that was, but it impacted multiple parts of the city.

There was also a high PM event that started on Christmas eve and lasted several days. You can see the PM2.5 levels getting above 50 quickly on Dec. 24th in the PM graph. 23/

It is helpful to have access to local PM readings since at least here in Ontario the air quality health index (AQHI) is an average of multiple pollutants and doesn't properly account for fast rising PM events. 24/

As you can see from the Ottawa AQHI readings, when PM levels were at 52 ug/m3, the AQHI index only reached 3 which Canada considers low risk even for at risk populations ( ). 25/ canada.ca/en/environment…

The US EPA AQI standard has a PM2.5 specific conversion where the same 52 ug/m3 would be rated as orange which is unhealthy for sensitive groups and the slightly higher 60 ug/m3 from Dec. 18th would be rated as red or unhealthy for everyone ( ). 26/aqicn.org/calculator

While there is no safe level of PM2.5, the WHO recommends limiting levels to below 15 ug/m3 to reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma ( ). 27/who.int/news-room/fact…

For people who are at higher risk of PM pollution, it is recommended to watch the PM levels directly and not just the AQHI level on its own. 28/

I also have a Model E indoor air quality (IAQ) which I used to measure multiple locations inside my house to see how much PM from outside was leaking in during the Christmas PM event and found some surprising results. 29/co2.click

Since you can download your raw Model E and X monitor data, you can use it to make custom plots overlaying PM levels to more easily compare PM detected in multiple locations in the house during the PM event. 30/

Using the Model E IAQ monitor, we discovered that an unfinished section of the basement had much higher levels than the rest of the house. It seems more air from the outside leaks into this part of the basement (see red line). 31/ Click "Show replies" 👇 to continue.

A finished section of the basement (yellow line) had half the PM2.5 levels as the unfinished section, and after we put a HEPA filter in that room the levels dropped by half again (blue line). A couple of bedroom areas on the second floor had similarly low levels of PM2.5. 32/

Here is the PM graph of the Model E in the basement hallway between the unfinished and finished sections. You can see the PM levels spiked up to 8 ug/m3 from the unfinished basement where the PM was leaking in. 33/

Sometimes just closing a door can make a huge difference and doing this quickly brought down PM levels to far below 1 ug/m3. Now we know during PM events to seal off that part of the basement from the rest 34/

It is not just external PM events you need to worry about. Cooking can also generate high levels of PM, and the Model X can be used indoors if you want. 35/

The two spikes you see in the graph are from microwave popcorn (PM 18 ug/m3) and cooking bacon inside an oven (PM 8 ug/mg) captured from the Model X in the hallway beside the kitchen. 36/

The PM also moves around the house from the kitchen, so please turn on any range/hood fans while cooking if you have them. 37/

Even the Model E in the basement picked up a similar level of PM from the microwave popcorn (PM 19 ug/m3) but much smaller amounts from the bacon (PM 2 ug/m3). 38/

The monitors also offer a nice feature that you can easily monitor your air quality readings remotely from a mobile device and even share the web link with other family members or friends if you want. 39/co2.click

The first is the public view which gives you a nice compact view of the most recent monitor reading along with graphs that show the patterns over the last 24 hours. 40/

You can choose to keep the link to the public view to yourself as well, only the owner of the device can generate a public view link. 41/

The second is helping others by making your sensor data available publicly on an air quality map. Businesses and organizations may want to report their indoor CO2 levels to the public so people know they take good ventilation seriously. 42/co2.click

Everyone can report their outdoor air quality levels so people who live in the area or will be visiting can get a better idea of the current state. 43/

The map is completely optional and can be enabled in the portal by going into the device "Configuration" and then choosing "Yes" for "Make this sensor public on the map". Selecting a location on the map creates a 2km wide circle for your monitor. 44/ co2.click

If you are a business you can select your exact location which will show in the centre of the circle. If you are a homeowner but don't want to reveal your exact address, you can click on a location near your home... 45/

... such as within the 2km sphere so that people know what part of the city the air quality readings apply to. 46/

It is important to then select if your sensor is located Inside or Outside, you can give your sensor a descriptive name, and also choose if you want to make your public view link available from the map. 47/

sensors that opt-in for the map can be seen here ( ). There are filters to only show CO2 or PM sensors, and indoors or outdoors to help find information more easily, and colours to represent concentrations measured. 48/ co2.click
portal.co2.click/map.html

Clicking on the circle of a sensor brings up the latest readings and if enabled, a link to the Public View. 49/

What about the cost? The Model X outdoor AQ monitor is $199 Canadian dollars and currently free shipping to Canada and the continental USA ( ). 50/co2.click/products/Model…

The Model X will use any USB-C power adapter but if you need one, they can be purchased for $10 (USA/Canada) or $15 (Europe/UK/Australia/NZ) when ordering. 51/

On the other hand, importing a PurpleAir AQ monitor to Canada is much more expensive and costs $229 USD for the monitor (without power adapter) and $29.77 USD in taxes which converts at current rates to $343 Canadian dollars. 52/

Someone who purchased one also got hit with $58 in import duties so a total of $401, almost 2x the price of a Canada built Model X. 53/

Right now until the end of Dec. 31st, you can get another 15% off any of the AQ monitors for even more savings using the code 2023END ( ). 54/co2.click

https://twitter.com/IndianaTux/status/1741127892061376577

For further reading on PM related pollution. The importance of indoor air quality ( ). 55/

https://twitter.com/jeffgilchrist/status/1607379781892575234

Fun with Particulate Matter (PM) Sensors ( ). 56/

https://twitter.com/jeffgilchrist/status/1648452264351383561

Wildfire PM2.5 Air Pollution and Equivalent Cigarettes ( ). 57/

https://twitter.com/jeffgilchrist/status/1672979098778456066

Wildfire smoke - now extra toxic plumes from sun UV ( ). 58/

https://twitter.com/jeffgilchrist/status/1675174138741178371

Ontario's Air Quality Health Index (AQHI) does not detect quick changing PM levels ( ). 59/

https://twitter.com/jeffgilchrist/status/1675174177374863364

@threadreaderapp please unroll