Geiger Counter Buyer's Guide

Since the days of "duck and cover", technology has made radiation detectors, or Geiger counters, as they are commonly known, much more accessible to the average consumer. Indeed, there is a wide variety of radiation detection devices available nowadays.

But how to choose? The purpose of this guide is to give you some background information on the technology, and more importantly what to look for when considering the purchase of a quality radiation detector.
First, what does a Geiger counter do?

The Geiger counter is named after the Geiger-Mueller tube. This tube is the core component of the device. It contains a thin metal wire through its center. The space in between is sealed and then filled with gas. The wire will carry a charge of ca. +1000 volts relative to the tube.

In measurement mode, ions or electrons penetrate the tube. As these particles enter the rube they tear electrons from atoms in the gas. Because of the high positive voltage of the central wire, the electrons are then attracted to it. During this process, they gain energy and then collide with other atoms thereby, releasing more electrons which cascades into a waterfall to produce an easily detectable pulse of current.

The reason the device is called a counter is because every ionizing particle that passes through the detector tube will produce an identical pulse which will be counted electronically.

This pulse is can be displayed with a light flash and/or audible a click, while other counters may pass the pulse to computing circuits and digital displays.

What is ionizing radiation?

Ionizing radiation consists of high-energy particles, which can detach an electron from an atom or molecule. This ultimately alters or destroys the atomic structure. However it is its effect on human tissue that makes this type or radiation so dangerous. High levels can break down the cell structure on a molecular level, while random particles from low dosages can alter cell DNA structure increasing the risk of cancer. Radiation emitted in proximity to soft unprotected tissue, such as found in the human lung, is particularly dangerous.

What are the three types of ionizing radiation?

Alpha Particles – This type of radiation consists of charged particles that are emitted from the nucleus of an atom in the process of decaying. These positive charged particles are quite dense, which stops them from penetrating through more than an inch of air or a sheet of paper. Alpha particles are not a serious health hazard, unless they are emitted from within the body, which will damage sensitive living tissue.

Beta Particles – This type of radiation consists of negatively charged particles from an atom in the process of decaying. These particles are light and can penetrate deeper than Alpha particles, but still not enough to be a serious health hazard, unless ingested, which causes damage to tissue. Beta radiation can only penetrate through a few millimeters of aluminum.

Gamma Radiation – Gamma rays are an extremely high-energy form of ionizing radiation which have a shorter wavelength than visible light. Because of the high energy and the difficulty in shielding against it, Gamma radiation is important to detect and avoid. It is by far the most dangerous of all radiation types. This is because Gamma radiation can penetrate deep inside the body and affect the vulnerable soft tissues such as bone marrow.

Why purchase a Geiger Counter?

• Detect leaks and contamination.


• Protect against radiation in or near a nuclear power plant.


• Check to see is groundwater has radiation.


• Protect food or products from radiation in warehouses or transport areas.


• Check an area for personal exposure.


• Test for potential radioactive materials.


• Check internal medical test levels (iodine-125).


• Monitor environmental air and water quality.


• Comply with mandatory safety regulations.


• Determine the origin of dangerous radiation.


• Determine radiation levels at landfills and dumps.


• Household items can contain ionizing radiation, such as smoke detectors.


• Detect uranium for collecting, or mining purposes.


• Hazardous materials or emergency first response.

What features should I look for in an effective Geiger counter?

Listed below are some features you should look for when considering which Geiger counter you should purchase.

1. Geiger-Mueller Tube – Avoid counters using old ion chamber technology such as vintage 1950's detectors. Geiger tubes have been around a long time and are highly accurate and reliable.

2. Audio Alert Function – This should have a user programmable threshold alarm that warns you of excess dosage levels. An audio readout will usually sound one “click” for each particle count. The audio readout will almost sound like static from a radio if there is a large number of particles that occur in a short time span.

3. Audio Off - This is a switch that will disable the Audio, while leaving the handheld radiation detector on and continuing to monitor radiation through a visual display.

4. Tested Precision Instrument – Be sure that the radiation detection instrument you purchase has been tested and certified by a recognized testing facility.

5. Radiation Types – This feature measures alpha, beta, gamma. Make sure that the radiation monitor detects all of these types.

6. Low Power Consumption – Choose a Geiger counter that uses minimal power or has a built in battery that lasts for at least five years. You don't want to worry about changing batteries if there is ever an actual public safety emergency.

7. Menu Control – The Geiger counter you select should have a simple, easy to comprehend menu that will guide you through the measurement process.

8. Information Storage – This feature is important because it accumulates radiation counts over a period of time instead of the standard button setting that only displays the radiation levels at that particular moment. This feature is helpful in determining longer term exposure.

9. Computer Evaluation – There are Geiger counters that can be downloaded and evaluated on your laptop or PC. Time sequencing is a great way to visualize radiation variability

10. Size Matters- Geiger counters do not have to be big and bulky. Find one that is compact, shock resistant, light, and easy to carry. If a carrying case is available, get it!

11. Analog and Digital Display – The display should express the radiation level both graphically as well as numerically. Sometimes analog is a better way to visualize relative changes in intensity levels.

12. Durability – Be sure the radiation detector you choose should be able to withstand extreme temperatures and the housing should not crack, peel, split or shatter.

13. Low Level Sensitivity - Your portable radiation detector should measure from below ambient radiation levels. A typical dirty bomb scenario would call for contamination at distance via fallout and for this you need to be able to detect relatively small changes above atmospheric levels.

14. Dual Measurement Units - The detector should express both metric and English units of measurement. By metric standards the unit of tissue dosage is uSv/hr or micro-Sieverts per hour. The U.S. standard unit is The mR/hr is milli-Roentgens.

15. Detection Measurement – The operating range of a radiation detection device is important when considering your purchase. A typical maximum operating range would be to 50 mR/r. This would detect radioactivity from a 1” or 2” piece of high grade uranium ore.

16. Airplane Portability – You will want your device to comply with FCC-15 standards so it will not interfere with radio transmission.

Remember, when deciding on a portable Geiger counter, be sure to find one that can detect all three types of radiation. And don't forget longevity. You want your device to have a long reliable life. Look for extended power - battery replacement after 5 years is a good benchmark. (Note: some companies will even replace your batteries for free.)