British Columbia

uSv/h CPM Date Past Reading uSv/h CPM
Vancouver   26  April 2015 Stanley Park 42
Horseshoe Bay
Surrey 16 Aug 4, 2017
Pitt Meadows  0.12 21  Sept 7, 2017 Sept 6, 2017  0.10  14
Abbotsford 0.10 June 1, 2016
Chilliwack / Cultus Lake 0.08 May 2016
Victoria
Campbell River  0.09  Feb 22, 2017
Tofino
Powell River
Prince Rupert

  

United States

uSv/h CPM Past Reading uSv/h CPM
Seattle, WA  0.099 33 Sept 7, 2017  Feb 2017  0.147 47
Ashland, OR 0.120 40 Sept 7, 2017
Sebastopol, CA  0.111 37  Sept, 7 2017  Aug 2017 0.141 47
Sana Cruz, CA  0.132  44 Sept 7, 2017  Sept 6 0.156 52
Palo Alto, CA 0.105  35  Sept 7, 2017 2015  1.395 466
Los Angelos  0.118 60 May 23, 2012
Haiku, Maui, Hawaii    0.084  28  Sept 7, 2017   Sept 2015  0.695 232
Kaneohe, Hawaii  0.140 Feb 20, 2014
Honolulu, Hawaii
Shrub Oak, NY 0.117 39  Sept 7, 2017  July 2017  0.180 60

  

Japan, China, Russia, Ukraine

uSv/h CPM Past Reading uSv/h CPM
Fukushima, litate  0.324 329 Sept 7, 2017  Sept 2016  2.730 329
Fukushima, Kamata  0.222  74  Sept 8, 2017  Aug 2017  0.883 295
Tokyo, Setagaya  0.168  56  Sept 7, 2017 Jan 2017  0.231  77
Hong Kong, China  0.204
 68  Sept 8,2017  Sept 5, 2017  2.099 701
     
Taiwan, Taipei 0.111  37  Sept 8, 2017       2015 0.701 
 234

 

Geiger Counter Readings are from various sources :  

Safecast.org   gmcmap.com    QuardraRad.com 

 

 

MEASUREMENTS : Units of Ionizing Radiation

This is an ongoing collection of conversion factors used to change a radiation reading into another type of measurement.

Picocuries per liter (pCi/L) multiply the amount by 0.037 to get becquerels per liter (Bq/L)

What is a Sievert? http://en.wikipedia.org/wiki/Sievert
What is a Gray? http://en.wikipedia.org/wiki/Gray_(unit)
What is a Rad? http://en.wikipedia.org/wiki/Rad_(unit)
What is a Curie?  http://en.wikipedia.org/wiki/Curie_(unit)
What is a Becquerel? http://en.wikipedia.org/wiki/Becquerel_(unit)
What is a Roentgen? http://en.wikipedia.org/wiki/Roentgen_(unit)

http://www.fukuleaks.org/web/?page_id=5675

What Is CPM in Radiation? - SOEKS

Posted by soeks-usa.com on 

What Are Counts Per Minute in Radioactivity?

When you get a Geiger counter and are learning how to use it, you’ll need to know about CPM, which is the counts per minute that you’ll see displayed on the analog meter in addition to the corresponding level of radiation. You might sometimes see counts per second, or CPS, instead, or you can easily convert from CPM to CPS if you’d like by dividing your CPM value by 60. So what is the CPM reading all about?

How Does CPM Work?

The counts per minute measurements are generally used to pick up the amount of particles around, which could include alpha or beta particles. A different level of measurement tends to be used for rays, including gamma rays and X-rays.

Instead of showing how much radiation something is giving off, the CPM radiation levels tell how many detection events the meter picks up. So the CPM amount doesn’t show you the amount or strength of the radiation. The device that you’re using to measure radiation can then also tell you the dose rate, although the conversion from CPM to dose rate will vary based on your specific device and some other factors, such as the kind of radiation. A Geiger meter uses energy compensation to create a reading of the dose.

While the measuring rate is “counts per minute,” the device often takes a sample from less time than the full minute and then determines what the total would be for the minute based on that sample.

What Does the CPM Value Mean?

Once you get your CPM reading from your device, you then need to figure out what that reading means. What are normal radiation levels CPM and what are dangerous ones? If you have your Geiger counter calibrated to Cs137, which most are, 1 milliRad per hour would equate to 1,200 CPM on your counter. At the same time, 1 microSievert per hour would equate to 120 CPM on the reading. These are more universal units of measurement that can help you better understand your radiation exposure.

A CPM reading of at least 100 is considered a warning level by the Radiation Network, although the length of time you’re exposed to the radiation is an important factor. If you’re concerned about staying within safe radiation levels, Ken Jorgustin explains on the Modern Survival Blog that it would take 432 days at a CPM of 100 to up your chance of getting cancer to odds of 1 in 1,000. At higher exposure rates, it would take less time. For instance, it would only take four days to increase your rate to those odds if you’re exposed to a level of 10,000 CPM.

When you use a Geiger Mueller detector, you’ll be able to easily see the counts per minute of radiation in a certain area. This can help you understand more about your environment and your exposure.

Units of Measurement (Radiation)

rad = 0.01 gray (Gy)
gray (Gy) = 100 rad

rem = 0.01 sievert (Sv)
sievert (Sv) = 100 rem

Rad and Gray are ‘absorbed dose’ units.
Rem and Sievert are ‘equivalent dose’ units.

Why a Rem and a Sievert?

They relate to biological damage done to human tissue and factor the differences between types of radiation. A multiplication factor is used that represents the ‘effective’ biological damage of a given type of radiation. This is the main reason for these units – to factor the differences in damage that is caused from one type of radiation to the next.

Radiation Factor (QF Quality Factor)
(1) Beta
(1) Gamma
(1) X-ray
(10) Nuetron
(20) Alpha

For example, the list above shows that a ‘rad’ or ‘gray’ unit of ‘Alpha’ energy that is absorbed by soft human tissue does 20 times more damage than a ‘rad’ or ‘gray’ of Gamma, X-ray or Beta radiation.

Radioactivity or the strength of radioactive source is measured in units of becquerel (Bq).

1 Bq = 1 event of radiation emission or disintegration per second.

One becquerel is an extremely small amount of radioactivity. Commonly used multiples of the Bq unit are kBq (kilobecquerel), MBq (megabecquerel), and GBq (gigabecquerel).

1 kBq = 1000 Bq, 1 MBq = 1000 kBq, 1 GBq = 1000 MBq.

An old and still popular unit of measuring radioactivity is the curie (Ci).

1 Ci = 37 GBq = 37000 MBq.

One curie is a large amount of radioactivity. Commonly used subunits are mCi (millicurie), µCi (microcurie), nCi (nanocurie), and pCi (picocurie).

1 Ci = 1000 mCi; 1 mCi = 1000 µCi; 1 µCi = 1000 nCi; 1 nCi = 1000 pCi.

Another useful conversion formula is:

1 Bq = 27 pCi.

Becquerel (Bq) or Curie (Ci) is a measure of the rate (not energy) of radiation emission from a source.

 

How much radiation is too much? – PBS

Converting-cpm-to-microsieverts