Note: This is a work in progress
Here in Iowa, we have radon and while the detection and mitigation of radon is simple, I wanted greater peace of mind. The detection of radon started with a kit I bought at Lowes. The kit was essentially a carbon filter I left exposed in my basement for a period of time, then the kit is shipped off and analyzed by a lab. When the lab indicated my radon levels were at the upper threshold levels I had a radon mitigation system installed. The mitigation system is really just a fan with a pvc pipe that goes through the cement slab in the basement. If the slab is sealed, the radon is pulled through the fan and up vented out through the roof of the house.
Just as the sump pump is simple in operation, there's a lot to be desired if something were to go wrong, which of course happened. Last winter water pooled in the p-trap of the vent pipe and froze. The ice interrupted the fan which tripped the GFCI outlet. Needless to say, there was no warning that the fan discharging toxic gas had been off for days; it was happenstance I even checked it.
Since I can't directly monitor the radon levels, the next best thing is to monitor the radon mitigation system. The only indicator the fan is working is a manometer attached on the vent pipe which is great news because a differential pressure transducer can be used in place of the manometer and read with an Arduino.
The differential pressure transducer acts the same way the manometer does - one opening is exposed to the air pressure inside the vent pipe and the other opening is exposed the basement air pressure. Then simply determine the difference. Once I have the data on an Arduino, I can send it over WiFi and Bluetooth and be notified as soon as the fan goes out.