Longmont Radiation Monitor
Last Overview Update: 2012-05-12
Overview
This is an indoor radiation monitor setup in Northeast Longmont, Colorado, USA.
The
detector is located sub-ground level near a window. Radon gas is a
steady 1.2 pCi/L. Above-ground indoor vs below-ground indoor testing indicated no appreciable differences during several
test runs. Therefore, the measurements here should represent the worst case
indoor exposure.
The detector is a Libelium made Radiation Sensor Board for Arduino. It's mated to an Arduino Uno and hooked up via a 25 foot active USB cable. The Arduino is running this sketch. On the host computer, this python program
is running which reports the values to both Twitter and Cosm (i.e. Pachube). The
values are collected once every 10 minutes and published. The Arduino's
on-board code keeps track of the real-time running average.
This detector is run by Joey Stanford. He also runs the Ute Creek Golf Course Weather Station.
Measurement Interpretation
Colorado is normally two to four times over natural radiation predominately due to altitude but in some areas due to radioactive ore and radon gas. Brief spikes as high as six times over have been noted and matched up using a SID array to solar flares. If you monitor the real-time values you'll see them drop slightly during the night and be higher during the day due to naturally occuring solar radiation. You can explore recent flares via the awesome SID Database Browser.
Don't be alarmed by high Count Per Minute (CPM) values or high "times over natural radiation" figures. CPM varies by detector and as such is not a reliable measurement. The "times over natural radiation" figure is not (in a practical sense) that important because of the small scale we're dealing with (e.g. 4 x 0.23 is still a small number especially since we're measuring in Microsieverts (vs Milisieverts or even Sieverts).
The key number on this page is the Microsievert (μSv) number. Natural background radiation is 0.23 μSv/h. This monitor reads on average about 0.69 μSv/h (2011) and 0.73 μSv/h (2012). 100.00 μSv is equivalent to a chest x-ray. So about once a week you get a chest x-ray's worth of radiation. In a normal year you're getting around 6044.40 - 6394.80 μSv (+/- 10% for calibration errors). For comparison, a trans-oceanic airline crew receives about 9000 μSv a year. For some graphical representations of this please see xkcd's radiation chart and Dave & Matt's Radiation Dosage Chart.
Now, all of that said, not everything is due to solar flares. Some of it can be construed to belong to Fukishima Daiichi as announced in this disclosure.
Data Feeds
Historical Graphs
Other Sites