I thought I'd give the CO2 sensor another try. This time, build the casing as water tight as I can and as cheaply as I can. Thanks goodness the CO2 sensor wasn't permanently damaged. I just had to calibrate it using CO2meter's software.
2" pvc plug with cord grip
Inside I had to thin the top off with a router.
Trap adapter for the silicone membrane.
The adapter has a washer inside which I used with the membrane and silicone for safety measure.
The hardware: Arduino, CO2 senseAir K-30 10%, 5v fan, DHT-22 humidity & temperature sensor.
The fan is for circulation, and the humidity sensor is to alert me if it's too high or if a possible leak. The membrane is porous enough for H2O molecule to pass through. If the humidity is too high, I can remove the plug.
The fit was too snug and the board broke in half so I kept it.
Final product. I'm out of the CO2 game but I'll set up a yeast reactor in a bucket to test. I'll send the data to a mysql database online. I'll post the result soon.