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Dedicated maps are also availble for: USA World Japan Tokyo Europe Oceania
Typical background radiation levels for most of the USA are in the 5 to 28 uR/hr range. Readings can be higher for brief periods of time due to normal variations in radiation levels. They can also be consistently higher for areas at high elevations such as Colorado, or with larger natural deposits of uranium, thorium, radon, etc.
The readings on this page were obtained using one of the Black Cat Systems radiation detectors:
The detector is connected to an ordinary computer (Windows or Macintosh) running a copy of the Rad software and connected to the internet (dialup, cable modem, dsl, etc). Rad automatically sends the current radiation reading to the web server that hosts this site, which generates the map showing the readings for all radiation monitoring stations. Rad is included free with any of our radiation detectors.
A geiger counter lets you check the environment and items for radioactivity. You can use to check for the presence of radon on your house or basement, or even use it to go prospecting for uranium or other radioactive minerals. The GM-10 and other members of the geiger counter family can detect radioisotopes such as Polonium 210 which was used to poison Alexander Litvinenko.
A geiger counter works by detecting the ionization produced by a radioactive particle. Each time a particle of radiation is detected, the counter records this event. The number of events recorded over a period of time indicates the amount of radiation present. Often this is done over one minute intervals, resulting in the familiar "counts per minute" or CPM. The higher the CPM, the higher the radiation levels. You can read a more in depth description of how geiger counters work.
So, using the above example, the square root of 16 is 4, so the standard deviation is 4. 3 times 4 is 12. So we would expect the readings to be 16 +/- 12, or range from 4 to 28. That is to say, even if the radiation levels are a "constant" 16, the apparent readings of the geiger counter will range between 4 and 28. So if you suddenly see the reading jump from 16 to 25, that does necessarily not mean that the radiation level has increased.
There is a writeup about Counting Statistics available.
Radioactivity is the emission of energy from the nucleus of certain nuclides or elements. Some naturally occuring radioactive elements include uranium and thorium and radon. A small amount of naturally occuring potassium is even radioactive.
There are three types of radioactive emissions:
You may be interested in Information on Radiation Units and Background Radiation Levels for more details about the various units of measurement for radiation, and some of the sources for naturally occuring radiation.
We also have an interesting page about Radioactive Products and Other Sources Of Radiation. Many apparently harmless products are actually quite radioactive! With one of our a href="http://www.blackcatsystems.com/GM/">geiger counters you can inspect items that you own for radiation.
Be sure to visit our home page, http://www.blackcatsystems.com We have a variety of software programs available for the Macintosh, Windows, iPhone, iPad, and iPod Touch. You'll be sure to find something of interest.
Users of our detectors are welcome to add their site to the map. Contact us at info (at) blackcatsystems (dot) com for details on how.
Several users have graphs of readings on their own websites, using the Rad software that is included with our detectors: