This is the first in a series of articles about using CO2 devices to monitor indoor ventilation and a look at several DIY projects building those devices. At the start of the pandemic, we covered the manufacturer’s response to citizens in a series of articles and videos we called Plan C. As we now anticipate a gradual return to normal activity nearing the end of the pandemic, we call this new series Plan CO2 – How We Could Safely Get Back Together.
Schedule C02 LIVE: Visit us on Friday April 23rd for discussions and demonstrations on monitoring CO2 devices. Show us what you’re working on or learn how to get started. Register here for this Live Zoom session on April 23 at 12 p.m. PDT / 3 p.m. EDT.
Many students are now starting to go back to the classroom, but few are equipped like Odessa Schulz, an 11-year-old who lives in Montreal, Quebec. When her school reopened after the New Year break, Odessa carried a homemade electronic device her father had made to measure and display parts per million (PPM) levels of carbon dioxide (CO2) in the classroom.
After Odessa took the reading, she drew it on paper and brought it home. In the evening, Odessa and her father Stephan Schulz analyzed a table with the measured values for the day, in which the measured values were recorded over time. Every night he recharged the device’s battery and Odessa left the next day with the device in her backpack.
You can see CO2 build up as students sit down in the classroom. You could see when they went to lunch and when they came back. For Stephan, the CO2 monitor was able to determine if the classroom was properly ventilated, which meant that windows and / or doors were open when the readings were below 1000ppm. In Quebec in January and February, if the windows are open at -20 ° C, the classrooms are cold. The students wore masks and hats in the classroom, tweeted @ stephanschulz3.
On February 5, the local Montreal television news reported on the Schulz family, the device Stephan had made, and his daughter taking it to school. Odessa told the reporter that the device “basically says how much CO2 is in the air – if it’s over a thousand, that’s not good because there isn’t enough fresh air.” She explained that the device is on the wall in the classroom and she can go over and read. It made her feel more secure. Jennifer Dorner, her mother, also felt better when she had data on her daughter’s classroom ventilation.
This message about the device he built, Stephan reminded, “really helped people realize that aerosol particles could be something worth studying and paying attention to.”
Unprepared to go back to school
The schools were busily disinfecting surfaces in the classroom and around the school because that is what they normally would. However, the evidence for the coronavirus was that it spread through airborne particles or aerosols. (The Diamond Princess Cruise Ship was practically the experimental laboratory that showed that the virus spread through the ventilation system, not on contact.)
Stephan Schulz and Jennifer Dorner have two children, 11 and 12. “They went to school the longest,” he said. “Then there was a time here in Quebec when they stayed home and recently came back. And with the feeling of discomfort, we leave them behind. ”
Stephan realized that his children had to see their friends: “So I think it was worth the risk,” he said. Even so, he was bothered by the government’s response to the pandemic. “It always seemed like the government, Canada and Quebec were very slow to incorporate what scientists have been saying the longest,” he added. At first it was the mixed message of wearing masks that made no sense, so he and his family started making them at home and passing them on to friends.
Stephan started learning about science himself and thinking for himself what was the best thing he could do for his family. He started thinking about monitoring aerosols indoors by measuring CO2.
Outdoor air quality sensors measure CO2 and the base measurement is around 400 ppm. If the space in a classroom were properly ventilated, the CO2 levels inside would ideally match the outside air. In a classroom of 20 to 30 people, if the windows and doors were closed, CO2 levels would increase and higher values can be used as a warning to indicate that there are more aerosols in the air. By monitoring indoor CO2 in a classroom, teachers and students can be reminded that they can reduce CO2 by simply opening windows and doors and leaving them open. The CO2 monitor makes these invisible aerosols visible.
Construction of a CO2 device
“I am a trained media artist,” said Stephan, who grew up in East Germany and came to Canada to do his Master of Fine Arts. “I do a lot of coding and software every day. Electronics like Adafruit and Sparkfun as well as Tindie are very familiar to me. “He noted that building devices by connecting components is a“ Lego-like system ”. He decided to build his own CO2 monitor.
“Arduino code is pretty accessible for someone like me to do something like this,” he said, adding that he always had an interest in science growing up. His favorite show was MacGyver.
Article in the German edition of Make:
During his research he came across the work of Guido Burger, a German manufacturer and engineer who lives in southwest Germany. Guido had developed and shared a project called “CO2 Ampel”. The CO2 traffic light project (“The CO2 Warner for Schools”) was published in 2020 in the German edition of Make: Magazine. Complete instructions in German and English were also made available on a university website.
To monitor CO2, Guido used the SCD-30 CO2 sensor from Sensirion, a Swiss company. (There are other options.) This is a two-channel optical sensor that uses two lasers to detect CO2 particles. At Adafruit, Stephan found the SCD-30 CO2 sensor mounted on a circuit board that can be easily connected to an Adafruit Feather M4 Express. He added a battery and a small OLED display. It’s not a complex device, but it’s not cheap. Stephan said the components cost him around $ 200.
The CO2 device is carried as a trailer. The SCD-30 CO2 sensor is located at the bottom right.
His first version of the CO2 device displayed the reading but did not log any data. That is what his daughter Odessa would do on paper. “It was actually a nice exercise for her to explain to her classmates and teacher what she’s actually doing there and to follow the scientific rigor of writing things down every 10 minutes,” he said. “I could see the levels were very low when I went to school and then higher in school, but luckily they never went above 1000 ppm,” he said.
Shortly afterwards, Stephan added an SD card so that the device began to write the data from the readings taken every 30 seconds. Graphing the data became easier, an automated task.
Annotated diagram and table display of the data from the CO2 monitoring device
Monitoring of CO2 in the classroom
I asked Stephan if his daughter had any concerns about carrying this device to her school. “My kids have been into media art for all of their lives,” he said. “You come to the installations and know that we solder at home every now and then. So she was absolutely thrilled. “You can see that Odessa was involved in making the device.
“She likes to bring new things to school and then has to explain it to her teacher.” I also wondered if the school and its teachers are open to having such a device in the classroom. “We were not sure. Usually the school is not very open to parents bringing in new things, but interestingly the teacher is very fond of it. “
Once, when Odessa didn’t bring the CO2 device to school, the teacher said, “Oh, where is it? Please bring it with you. “Stephan believes that monitoring CO2 provides some assurance that everything is okay. It gives feedback about whether the windows and doors should stay open and how long they can be closed. It can encourage certain behaviors that could be seen as positive changes.
When you noticed the patterns and the actions taken to make the changes required, it became clear to Stephan that there was no need to bring the device into the classroom every day. Stephan asked friends if their children should bring a device into their classroom. “One of our friends, when their daughter took it to school, the school said, ‘Oh what is that? No, you can’t have that, put it back in your locker. “Stephan thinks they were afraid of the information it might reveal. The classrooms at school had no windows
Stephan said he had difficulty understanding why institutions like schools “are afraid of too much information. Personally, I give myself more. I can filter. “He believes that in an institution everything has to be done officially. “Quebec did that. They ended up going around with proper sensors and scientists and collecting the information, but it’s so slow. “
“You should allow parents or citizens in general to do something other than sit on the couch and wait and see. They should allow us to collect information and be happy to have it collected and used, even if it’s just a snapshot or pollution. Even with a lot of dirty information and a lot of noise, you can end up filtering out a signal, ”he explained. There is room for amateur scientists, he added, amateurs, what can be doers.
The friend’s school that refused to allow the device eventually came by. Stephan said, “The city or province came over and did proper testing. And even though it was a room with no windows, the quality was actually much better than expected as they had a central air exchange system. “
Share your work
Stephan shared the building instructions and the code on Github for his CO2 project. He doesn’t build a kit because this project is a reflection of what he can do himself and with his family. It was a means of understanding what was happening during the pandemic and doing something about it.
In Part 3 we will look at the work of Guido Burger, but here we see the basic elements of the CO2 device and its application:
- Hardware – a microcontroller that connects the following components
- A CO2 sensor
- A display for displaying the measured values
- A data logger or, alternatively, a wireless connection to collect and share data.
- Read the sensor and write it on the display
- Logic in connection with different CO2 values
- Graph of the data
A display – the bigger the better – helps to make the measured values available to everyone in the room. This is the focus of the project by Carter Nelson, who developed and documented a CO2 project for Adafruit. We’ll cover it in Part 2: Make A Big Public Display.
Credits: Photos and diagrams by Stephan Schulz