In this project I've created a co2 sesor (mh-z19) with connection to a mqtt broker, so you cann send the co2 data to a mqtt broker.
I've used the esp8266 12e version.
Folder structure: firmware - all files, that you do need to flash your esp8266 12e pcb - board schema, pdfs. Imprtant: for the board you need a usb-connection board (show image board_top.jpg) 3d-models - 3d models for 3d printer, so you can print a case for pcb.