Last sunday I wrote I would have attempted a Radon measurement with and without the Autunite crystal "sooner or later".
In the end I couldn't resist and I started one the very next day.
As I said before I am currently monitoring the bedroom of a house made of tuff. The room is at the upper floor of the house so Radon from the soil is not a factor there. I am using an active detector in order to have a continuous radon monitor.
Tuff is a pretty common building material in Italy (well, it was more common in the past than it is now, but there are still a lot of buildings made of tuff around) but I suspect it's not as well known in the rest of the world. So for those who want to know why a tuff building should be interesting at all as far as radiation in general, and Radon in particular, is concerned you can read this post where I tested some Tuff blocks used to build this very same building
viewtopic.php?f=5&t=520
I first measured the Radon level after a period if 3-4 weeks when door, window and shutter of the room had been constantly closed with very little air change. Nobody is living there in this time of the year.
As a result Radon built up inside the room and I got a week average of nearly 400 Bq/m3. Unfortunately I don't have the photo of this measurement.
Later on I left the detector there but providing an air change of roughly an hour once a week while leaving the window open (but the shutter still closed), providing a small but constant ventilation, and the level decreased to 200-220 Bq/m3 and held stable for several weeks now. With a normal use of the house during the summer months the level is likely between 100 and 200 Bq/m3, so not a worrying one.
Here you can see what the weekly average was last monday, September 30. 205 Bq/m3.
On that day I took the 3.9 grams Autunite crystal, inside a plastic bag and a small polystyrene container, and put it in the room. The light of the photos is poor because I still kept the shutters closed (albeit open them for a minute or two woulnd't have made any real difference).
So here's the crystal.
And here's the room. You can see the window open with the shutter closed. The green circle highlight the position where the crystal was left, while the red cicle is the where the detector is. Being a bedroom I figured out the most significant place would be at the same height from the ground as the person sleeping there would be, so the bedside table was perfect for that.
The room is about 15 square meters with an average height below 3 meters, therefore we are talking of roughly 40 cubic meters.
After six days the weekly average barely moved, albeit this is still an initial result it doesn't seem like the presence of the crystal is having a significant impact so far. A 5-10% oscillation is perfectly normal considering the changing weather.
I think one day I'll do a thread on this measurement I currently doing, with the gamma spectrum of the room and a dose assessment from both gamma radiation and Radon.
When the temperature will go down in winter I will close the window, stop the weekly air changes, and let the Radon build up again.
Massimo
