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Build a simple device that warns if CO₂ concentration in a room becomes a risk for COVID-19 aerosol infections.

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CorO₂Sens

Build a simple device that warns if CO₂ concentration in a room becomes a risk for COVID-19 aerosol infections.

  • Measures CO₂ concentration in room air.
  • Controls an RGB LED (green, yellow, red, like a traffic light).
  • A buzzer can be connected that alarms if levels are critical.
  • Also opens a WiFi portal which shows current readings and a graph (not connected to the internet).
  • Can be built for ~ $60 / 50€ (parts cost).

This project was heavily inspired by ideas from Umwelt-Campus Birkenfeld.

You can also find a good overview of the topic by Rainer Winkler here: Recommendations for use of CO2 sensors to control room air quality during the COVID-19 pandemic.

coro2sens overview

Sensors

  • The sensor used here is the Sensirion SCD30 (around $50 / 40€) which is optionally augmented by a BME280 pressure sensor to improve accuracy.
  • Look here if you want to use MH-Z19B sensors.

Threshold values

LED color CO₂ concentration
Green ("all good") < 800 ppm
Yellow ("open windows") 800 – 1000 ppm
Red ("leave room") > 1000 ppm

Based on a Recommendation from the REHVA (Federation of European Heating, Ventilation and Air Conditioning associations, rehva.eu) for preventing COVID-19 aerosol spread, especially in schools.

Web server

You can read current levels and a simple graph for the last hour by connecting to the WiFi coro2sens that is created. Most devices will open a captive portal, immediately showing the data. You can also open http://10.0.0.1/ in a browser.

You need

  1. Any ESP32 or ESP8266 board (like a WEMOS D32 (about $18 / 15€) or WEMOS LOLIN D1 Mini (about $7 / 6€)).
    ESP32 has bluetooth, for future expansion.
  2. Sensirion SCD30 I2C carbon dioxide sensor module (mouser, digikey) (around $50 / 40€).
  3. 1 NeoPixel compatible RGB LED (WS2812B, like the V2 Flora RGB Smart NeoPixel LED, you can also remove one from a larger strip which might be cheaper).
  4. A 3V piezo buzzer or a small speaker.
  5. Optional: Bosch BME280 I2C sensor module (like the GY-BME280 board), for air pressure compensation, improves accuracy (less than $5 / 4€).
  6. A nice case :) Make shure the sensor has enough air flow.

Wiring

ESP8266 pin ESP32 pin goes to
3V3 3V3 SCD30 VIN, BME280 VIN
5V 5V LED +5V
GND GND SCD30 GND, BME280 GND, LED GND, Buzzer (-)
SCL / D1 SCL / GPIO 22 SCD30 SCL, BME280 SCL
SDA / D2 SDA / GPIO 21 SCD30 SDA, BME280 SDA
GPIO 0 / D3 GPIO 16 LED DIN
GPIO 14 / D5 GPIO 19 Buzzer (+)

Flashing the ESP using PlatfomIO

  • Simply open the project, select your env (esp12e for ESP8266 / esp32dev for ESP32) and run / upload.
  • Or via command line:
    • pio run -t -e esp12e upload for ESP8266.
    • pio run -t -e esp32dev upload for ESP32.
  • Libraries will be installed automatically.

Flash using the Arduino IDE

Please let me know of any issues you might encounter (open a GitHub issue or write me on twitter.com/kmetz or k@kjpm.de). Also, I'd be for hire for customizations.