Version: 0.1
This project is based on other Arduino projects by Alex Gyver (RU) and Norovl (RU). All comments are still in Russuan but I'm going to translate it later
This firmware uses 1602 screen with big numbers as sensor values. In addition it has a Buzzer which plays melody once CO2 level reaches unhealthy value. There is also a Mute switch to switch off all sounds.