Uses MH-Z19 or MH-Z16 CO2 detector and DHT-22 (or DHT-11) Temperature/Humidity sensor to give air quality readout and actuate relays if CO2 level goes above 1000ppm (Lo Alarm for turning on extraction fan) and High Alarm at 5000ppm to sound an alarm etc. Uses large 20 x 4 HD44780 display Hardware is 100% Complete. Software is about 90% Complete (Works but untested and buzzer/silence not yet worked out) Will post code back here and on my website when 100% have attached Work In Progress MPLABX XC8 Code (incomplete but which will display CO2 levels) Has spare UART brought out to header to attach MODBUS/WiFi/Bluetooth if required. PCB footprint suitable for mounting in standard industrial 158x90x65mm Plastic Enclosure