This tiny radiation monitor is small - really, really small and exceptionally sensitive. It’s actually an old friend: we used to sell these by the bucket-load a few years ago, but then the supplies dried up and we thought we would never see them again. We obviously didn’t reckon with the occasional warehouse find and once again we are very pleased to offer this brilliant little gadget, but be quick, stocks are limited and we don't know if we'll ever get any more.

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They date from the early 1990s, and are another spin-off from the Chernobyl accident. They were made in the Soviet Union and they wisely used some of the best military grade components in this very capable little instrument. They have been in storage for some time but they are in excellent condition, and full working order but the cardboard boxes they come in may show some signs of wear.

There’s only one control, an on/off switch on the back and when it is on it emits a soft ‘confidence’ tick roughly once a second, so you know that it is working. When its miniature Geiger Müller tube detects radioactivity (Beta and Gamma) above a pre-set threshold it emits a beep and the red LED on the top flashes. The rate of beeps and flashes increases with the intensity of the radiation field it is detecting. A simple colour coded chart - see below - on the back of the case shows normal, elevated and dangerous levels as indicated by the number of bleeps and flashes per minute. Typically you will hear several beeps a minute from normal background radiation.

NEW! Special Edition 'English'  BIRI-1

We have commissioned a new and, we hope, smarter and more up to date set of front and back panel labels for the BIRI-1. The big news is they're in English, so you can tell straight away what the beeps mean and which way around the batteries go.  Numbers are limited so it's first come, first served; if you want one make sure that you tell us in the Message box on the Order Form, or send an email ( when you place your order.


If you want to keep it old-school here's a translation of what the original Russian back panel chart says:

Less than 12 count/min = Normal Background

12-24 counts/min = 60 – 120 uR/hr

24-60 counts/min = 120 -300 uR/hr

Continuous beep/flash = > 3000uR/hr

The outfit is powered by two 1.5 volt button cells and a pair are included, along with the original Russian instruction leaflet - we're also providing an English translation - plus one of our distinctive yellow lanyards, so you can hang it around your neck.

You can get an idea of just how small it is from the photo, that’s a One Pound coin standing next to it but if you prefer real numbers, here’s the basic specs:

Dimensions:                63 x 36 x 16mm
Weight:                         23 grams (50g with batteries)
Power Supply:             2 x 1.5 volt LR9 button cells
Detector:                      SBM-21 Geiger Müller tube

Detection range:         Beta & Gamma, 10 to 3000 uR/h (microRoentgens per hour)

Indicators:                    audible alarm and LED
Supplied accessories: 2 x modern alkaline button cells, neck lanyard, original instructions (in Russian), original mains charger & original A-06A rechargeable cells (see below)

It is powered by a pair of button cells and two modern equivalents will be supplied with the unit. We will also include two of the original rechargeable cells that came with it, and a mains charger, but only for historical purposes. We strongly recommend that neither are used. The cells are now well past their use by date, no longer hold a useful charge and prone to leakage and we are not confident that the charger meets current safety standards.


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Biri-1 Tiny Keychain Dosimeter

  • Product Code: Biri1 Dosimeter
  • Availability: In Stock
  • £79.99