One of the main project focus was to monitor air quality in my little home office. 

It should measure the air quality and remind me periodically to get some fresh Air into my little room. This should be done invisible for other people. Always keep in mind in all your Projects the WAF. If it is invisible the acceptance is higher.

The biggest challenge was to find a sensor that fits into this tight head room of my lamp that had only around 16mm of height. 

On the market are different sensors available that can output CO² Value or an equivalent eCO². CO2 is one measurement value to determine if the air Quality is good in a room. Scientist proofed that concentration goes down if the CO2 concentration in room is above a certain value.

"The level of carbon dioxide in conference rooms has a significant effect on the comfort of the working conditions (Tham 2016)."

At the beginning of the project I was not sure about the type of sensor I should use, which is best an which would be available due to Chip shortage.

So i deciced to make this module in my desk lamp as interchangable as possible.

Fortuanetly most of these Senesors are availible as a breakout board. And most of them have the same pinning

These Sensors have been in my focus:

SGP30(Temp, eCO2)

CCS811(eCO2, TVOC)

BME680(Temp, Humidity, Pressure, eCo2, TVOC,...)

All of these sensors can be controlled with I²C Protocol. This means you only need 4 lines (VCC, GNC, SCL, SDA) to connect to the sensors and read out data. And guess what: Pinning is identical for all 3 of them! What great News for a PCB Layout.

And Size is well below 20mm. :-) Perfectly fits inside my little lamp.

There are various Reports on the Internet which is best. I recommend this website for further studies

Here all of them are compared.