Pseudonymous hacker "polyfloyd" has shared a project which aims to turn a three-year-old event badge into a ventilation monitor for SARS-CoV-2 protection at Hackerspace Bitlair — using an MH-Z19 carbon dioxide sensor.
"Infections of SARS-CoV-2, the virus better known as the dreaded Coronavirus, can take place by inhaling airborne aerosols," polyfloyd writes. "The risk can be reduced by ensuring a constant supply of fresh air by, for example, just opening some windows. We at Hackerspace Bitlair, for which I carry responsibility as board member, wanted to find a way to know when we need to start ventilating our indoor spaces.
"And there is a way to do this! If we take the following into account: Virus aerosols are a product of exhalation; CO₂ is a product of exhalation. This relation implies that if we know the amount of CO2 in the air, we can use this as a proxy to estimate relative infection risk. Bitlair had one CO2 sensor based on the cheap MH-Z19b module, but this was not enough to rely on, especially because there are multiple rooms and we obviously can not measure through walls."
The solution: Picking up additional MH-Z19 sensors and attaching them to the SHA2017 event badge, which comes already equipped with an E-Ink display, six user-accessible LEDs, Wi-Fi connectivity, and the most important aspect of all: "We had about 6 left over from the SHA2017 event," polyfloyd explains, "which is enough for this project."
Having designed an add-on board to house the sensor and to provide a mounting point, polyfloyd had a working monitor which is capable of displaying current and historical readings, flash LEDs when the carbon dioxide levels - and by extension the SARS-CoV-2 infection risk — goes above a pre-set limit, and even push notifications via Wi-Fi. "Of course," polyfloyd notes, "it is up to the people present to actually open and close windows, but now they at least have some data to act on and take their own precautions."