We found unexpected trouble in paradise with our Arizona mountain home. The problem is excessive Radon. Radon is the second leading cause of lung cancer.
There is hardly any data (or awareness) about Radon in the sparsely populated county. When the EPA did its nation-wide Radon testing in the early 90's they may have only sent kits to about ten homes in the whole huge county.
I bought an Airthings air quality monitor and installed it in the living area of the house. It is on Wi-Fi so I can monitor remotely.
The air quality monitor detected Radon! I then bought a cheaper Airthings monitor (also with Radon support) and installed it in the garage. It uses the first device as a 'hub" so I can see it's data, even though it does not directly have WiFi.
Half of the space under the house is the large garage that I spent a lot of time with air sealing the walls, and the cracks in the floor, as well as painting the cinder-block walls using a roller, and making sure that paint got into any little voids. So the garage is much more air-tight now and no longer feels drafty during the winter. But this means that there is less natural ventilation.
The other half of the house is over a steeply sloped dirt crawl space. It is very primitive and I have been removing old brush (preserved since 1982!), surface rocks (just left there when the foundation ring was dug and poured), and other garbage. This is likely where a lot of the Radon is coming from.
Regardless, these are recent results from the garage. The green was from when we were there and had the windows open. They say that average Radon levels should be kept less than 2, but there have been peaks to 19 in the garage and 7 in the house. It is also said that Radon levels will be highest in the dead of winter as the "stack effect" draws more air from under the house as it rises.
