Geiger Counters

20th March
The UK's Foreign and Commonwealth Office is trying to confuse our supporters by lying about what Geiger Counters can measure - claiming that contrary to what LLRC says some can measure alphas. It's nonsense. Take note of it only to note that the authorities want to "keep the public confused", as President Eisenhower demanded of his own officials in the 1950s(ref.). See our comments on the FCO

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Original advice (16th March 2011)
People are asking for advice on Geiger Counters. In this emergency anything is better than nothing. There are lots of Russian Geiger Counters on ebay. Before you ask, we don't have a list of recommended models. With hindsight we ought to have researched this but we didn't get round to it and now we haven't enough time.

You need one that will measure down to background levels. This means it needs to be able to display 0.05microSieverts or MicroGrays per hour. Background should be about .05 to 0.1 microSieverts per hour (0.005 milliRoentgens per hour up to 0.01 milliRoentgens per hour).
"Civil Defence" models distributed during the Cold War are unlikely to be any use. We have seen adverts for the CDV-715, for example, which has a range with the bottom end starting at 0.01 Roentgens per hour. Natural background radiation should be in the range 0.01 milliRoentgens per hour down to 0.005 milliRoentgens per hour (1 milliRoentgen being one thousandth of a Roentgen). In other words the CDV-715 is 1000 times too insensitive to pick up even the highest likely value of natural background.
Do not worry about calibration (see footnote).
Don't wait until you think the fallout might have arrived. Take readings outdoors immediately to establish the baseline value of what's normal for your area. Note down the readings. Ideally, email us and tell us where you are and what your baseline reading is.
Keep taking readings regularly - several times a day. Don't panic if there's a small increase when it rains - that's normal. Take avoiding action (see below) if the reading increases to double the baseline value and at that point please tell us.

NOTE: We have said Geiger Counters cannot measure or detect the presence of alpha emitters like Plutonium and Uranium or beta emitters like Tritium and Strontium 90. This remains true but it is very likely that those contaminants will arrive together with gamma emitters like Caesium 137. To put it another way, if the gamma signal increases, make the precautionary assumption that it's a flag for the whole cocktail of radionuclides from the reactor and from the spent fuel rods that have been blown into the air or burned. Take what action you can:-

• stay indoors and keep doors and windows shut,
• drink bottled water (even if it's only tap water that you drew off and stored before the fallout arrived),
• use tinned milk,
• don't eat local produce unless it was harvested earlier.

Footnote on calibration: Purists and pro-nuclear critics will bitch about calibration (i.e. standardizing your instrument against a known radiation source). You must not worry about it. This is about public protection, so accurate values are nowhere near as important as any variations you find measured on your monitor. So long as you keep using the same Geiger Counter you have a reliable way of spotting the changes.