Radon and CO2

In parts of the world low levels of uranium ore is naturally in the ground doing its thing - breaking down and living its best half life.
The result of this is that humans then come along, dig a big deep hole and make the basement of their home, stacking the usual house on top.
The problem with this was not really discovered until sadly many decades later when people started to die horrible slow deaths of lung cancer and the numbers were too large to ignore.
Tracking backwards, it became clear that the natural breakdown of said uranium was radon gas and its really not great for humans to be sucking that stuff.

Its not heaver than air, it does not pool at the lowest point, it just hangs around much like air does. Since it occurs in the backyard of said basement house, its not an issue outside, it just seeps out of the grass and blows away in the wind.
The problem is just sits and builds up in the basement.
Open a window or two and the level goes down. How far down? Depends on the windows etc.

Over time, the powers to be (We are from the government, we are here to help) came to draw a line in the sand of 4 pCi/L (picocuries per liter) is 'safe' to breath for a lifetime and not die a horrible death.
Sadly, I don't have the time in this blog right now to dive into the detectors for this sort of thing, but they have a broad range of sensitivity and price. (Back in December I bought myself a Geiger counter).
Bottom line, if you live in an area with naturally occurring uranium ore in the ground and have a basement, get yourself a radon detector.
I've chosen airthings. (USA Amazon link)
Mostly because its well reviewed, global, affordable, they have more than just radon sensors (keep reading) and they have an API that will allow me to get the data out of their system and into my home monitoring system.

I've put one to use for a few weeks to let it soak. Radon is a low slow decay, so it does take at least 48 hours (for the expensive sensors) to get a rough baseline.
In the case of my sensor, full readings take 30 days from placement, but 2 weeks will show a pretty good trends of where things are at.
Here is my 1 week trend:

About a day and a half sitting on my window in California, nice and flat around zero. 30 hours offline while the airthings sensor was in the back of a u-haul truck.
Placed in the basement in Idaho and it slowly started to soak up the active partials and count them. Dotted line is the 1 week average, so in a few days time we are going to see that go up. Orange trend is getting close to the bad number 4. Red trend line is anything over 4.
Its going up and down as the windows in the basement, while closed, are not totally airtight. They are originals from 1970 when the house was built.
The upstairs also leaks air and so it slowly circulates down the stairs and dilutes the radon a tad.... So some oscillation is expected.
Its helpful for me to get this data now while no one is in the basement, walking around and stirring up the air.

Radon mitigation pretty much consists of sucking the air out of the basement and blowing it out above roof height where it can dilute into the air up high.
Its a simple as PVC pipe –> fan –> PVC pipe.
I wanted to get the baseline before and after readings so I can be sure the mitigation system is working and also continuously monitor it with an email alert should the fan etc stop sucking.

Of course, when I mentioned to my mates Gary and Dan about said sucking, Dan said 'where is the air coming from'... And its a great question with a simple answer. All those leaky windows are going to (in winter) be forced to draw in 30F (-1.1C) air and cool the warm house just so we don't die of lung cancer.

Which brings us to an unexpected sensor reading.... CO2.
Of course I followed my 'buy once cry once' mantra and got the most expensive airthings sensor that measures a whole bunch of other air quality data points.

Top one we have talked about, but, hey, what's that other red line?
I guess it should not have surprised me, its a basement with only 3 small windows.
How is any (fresh) air getting down there?
I'm not going to rush into things, money is a very real consideration when you don't have a regular 9-5 job and wage, but I do need to feel 'safe' when I spend 3-4 months a year (winter) working and perhaps sleeping in the basement.
Bottom line. The radon mitigation will stir the air, so we can keep an eye on the CO2 reading and if it does not go down, then we will have to look at an air-to-air heat exchanger.

https://www.amazon.com/dp/B00KG8SMHE

This is the one I have my eye on.
Since I plan to replace the basement windows and about half of the upstairs ones, I am mindful that we have to keep an eye on the air flow pressure manometer across the radon fan. (Anyone know of one with an API or analog output?) As I make the house more airtight, the radon fan is going to struggle to suck, so I end up a vicious cycle. Having data for the systems is important to make sure they work as intended.
Anyway, if the new windows cause an issue, I will look at the air-to-air exchanger and it should take the sting out of sucking cold winter air into the house.

I love basements, so yeah, all this is worth it. (To me)