OpenAQM

Open air quality monitor

The current (second) iteration measures:

• CO₂;
• PM₁ - PM₁₀ - particulate matter or, approximately, smoke;
• VOCs - volatile organic compounds (basically things which oxidise when heated);
• temperature, humidity and pressure;
• ambient light level;
• sound;
• and it has a PIR detector to detect whether a person’s nearby.

It has some outputs, too:

• a 12V PWM output to drive fans (requested by someone to drive the fans in a https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box)
• an RGB LED for a traffic light indicator
• an amplifier for a loudspeaker.

Some interesting results so far - it doesn’t take long for the CO₂ level to rise over 1000ppm in my bedroom (which is probably 20m2 with a vaulted ceiling) with just me in it, a gentle smell of pine smoke in the evening corresponse to PM_2.5 levels of 70-100ug/m3 (the EU standard is 20ug/m3 averaged over one year), taking a sip of wine and breathing over the VOC sensor makes it go nuts, and the unit’s very effective at detecting vaping.

Current status as of 2025-02-12: testing three CO₂ sensors against each other, and testing some of the features which weren’t on v1. Results of the CO2 sensor testing at CO2 sensors