I use this VINDSTYRKA air quality sensor from IKEA, mainly because of its price and accuracy. It is all connected to my Home Assistant and automatically turns on the air filter when the VOCs or Particle levels get too high, turning it off when back down to acceptable levels. It also turns on the filter after the print is done for 5 min to clear the air.
But its also great just to get a visual check of the air quality inside your enclosure, including temperature and humidity.
Since the sensor cannot have its back-side blocked, it needs to be mounted somewhat away from the side and back walls of the enclosure.
Assembly:
If anyone is interested, it uses the SEN54 module from Sensirion. A complete teardown of the sensor can be found here:
https://github.com/oleksiikutuzov/IKEA-VINDSTYRKA/blob/main/teardown.md
The author marked this model as their own original creation.