Seattle Washington
Live Radioactivity monitoring online - Realtime Geiger Counter

Smoothed plot of data over past 24 hours with absolute rate:

Hourly xtics

Plot of data over past 7 days:

Daily xtics 0:00 UTC

click grid icon in lower left of SVG graph to toggle grid lines

Click here for monthly and yearly graphs - Also available as PNG

The data collection was reset on February 26, 2019.

The 24 hour graph is updated every 15 minutes. The 7 day graph is updated every 6 hours.
This page will auto-refresh every 15 minutes.

(rate units / minutes) = mR/hr
1 uR = 0.001 mrem or 0.01 uSv
1 uSv = 0.1 mrem
1 mR = 1000 uR or 10 uSv
typical chest X-ray = 10 mrem
typical mammogram = 400 mrem

mRoentgen, millirem and mrem are equivalent terms
Sievert units depend on other factors such as the type of radiation (alpha, beta, gamma or X) and the effects on different parts of the body

The data for these graphs is obtained using a geiger counter connected to a Raspberry Pi.
The counter is manufactured by Aware Electronics, model RM-80, used to detect Alpha, Beta, Gamma and X-ray particles.

The counter is located east of Seattle in Washington.

Spikes in the readings can be attributed to radon gas being pushed out of the ground after locally heavy rains, or dubious particles carried in wind or clouds.

Helpful Links:

Understanding Radiation - Radiation Dose Chart

The graphs shown above display real-time monitoring of ambient wide-spectrum ionizing radiation.

Ionizing radiation is given off by the nucleus of an unstable atom in the process of reaching a stable (ground) state. Radiation from radioactive substances ionizes the matter it passes through (splits the molecules) into charged ions of alpha, beta and gamma particles. These particles in concentration can cause the formation of free radicals, DNA strand mutation and a variety of other unhealthy side-effects.

Tritium, a radionuclide emitted as waste from new-generation nuclear power reactors, passes through the human body in 12 days. However, when the radionuclide unites with carbon in the human body, plants, or animals, it becomes organically bound (OBT) and can remain in the human body for 450 to 650 days. One study found traces of tritium in the body 10 years after exposure.


In the United States, members of the general public annually receive an average background radiation dose of about 360 millirem (mrem, mR) from a combination of natural and man-made sources. The primary natural source, radon gas, contributes about 200 mrem, to the average annual dose equivalent, and medical x-rays, the primary man-made source, contribute about 40 mrem. (A typical chest x-ray results in a 10 mrem dose.)

The U.S. Nuclear Regulatory Commission(NRC) has established dose limits for workers exposed to radiation as part of their jobs, and these limits have been adopted (where not otherwise required) by the U.S. Department of Energy(DOE). The annual dose limit for radiological workers overall is 5.0 rem (5,000 mrem) whole body, and for declared pregnant workers, 0.5 rem(500 mrem) to the unborn child (embryo/fetus) over the nine-month gestation period. The average annual dose to the general public from nuclear industry activities is limited to 0.1 rem (100 mrem).

The NRC limits reflect the prevailing assumption among government (and industry and many academic) technical authorities that an individual must receive a whole-body dose of about 25,000 mrem (15,000 mrem for a pregnant woman) before there is a significant increase in the risk of serious human health effects, and a dose of about 500,000 mrem (500 rem) before probable death as a result of radiological health effects. On the other hand, government regulations also require that NRC licensees and DOE contractors follow the radiation control concept known as ALARA (As Low As Reasonably Achievable). The ALARA objective is to attain worker and public doses as far below the applicable limits as reasonably achievable given social, technical, economic and policy considerations. The ALARA concept recognizes the uncertainties associated with the risk of low level exposure to ionizing radiation. It should also be remembered that there is considerable technical controversy about the individual health effects of any additional exposures beyond background levels, and mythological debate about the use of collective population-doses to calculate latent cancer fatalities among the general population in probabilistic risk assessments.

Other online geiger counters:

National Radiation Map - USA

Chernobyl disaster photos by Elena Filatova

Jason Buchanan,
Updated: 26-Feb-19
This is a work in progress - please email any errors
Live Geiger Counter Data for Seattle area