How to measure radioactivity (ionizing radiation) - Geiger meter comparison guide

Easily measure the radioactivity of building materials, granite, medical equipment, from nuclear accidents, etc. with radiation meters, geiger counters, dosimeters that detect alpha and beta particles, gamma radiation, X rays etc. How to choose a measuring device.


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Not the type of meter you are looking for? Please check our guides on low frequency meters (measure radiation from power lines, cables, transformers, electric devices laptops etc), high frequency meters (measure radiation from cordless phones, wireless modems (Wi-Fi), cell phone masts etc) or check the frequently asked questions about electromagnetic field meters!

We advise you to read all the following information about how to use a radioactivity meter and which are the important features to look for, but if you are in a hurry to see the recommended meters go straight to the radiation meters comparison table at the end of the article.

What do radioactivity meters measure?

Radioactivity or ionizing radiation meters measure the radiation from radioactive materials (subsoil, food, building materials, tiles, granite counters, nuclear accidents, ionization smoke detectors, medical equipment etc.).

The most common radiation meters are Geiger - Muller counters, which can record most or some types of radioactivity (gamma rays, X, beta particles, alpha particles etc).

For measuring the proven carcinogen radioactive radon gas (which is emitted from the soil, enters buildings by pipes and cracks and especially accumulates in low floors with inadequate ventilation), we recommend the use of radon meters, digital alpha particle counters, radon detectors or dosimeters and not Geiger counters. Radon gas consists mainly of alpha particles which most Geiger counters do not measure or measure inaccurately.

Read more about radioactivity and its effects..

Which are the main sources of radioactivity?

  • Building materials with highly radioactive materials (eg various ceramic tiles, granite counters, bricks, cement, pumice stones of volcanic ash, phosphogypsum, etc.)
  • Food with radioactive residues (eg vegetables, milk, meat and fish from the affected areas of radioactivity in Japan and neighboring regions - anything produced after March 12, 2011).
  • Phosphorescent watches, pottery, ionization fire detectors etc.
  • Kitchens that run on natural gas
  • Water from wells
  • Nuclear plants and reactors, especially after a nuclear accidents
  • Waste materials from various industries, hospitals etc.
  • Very high altitude (higher levels of cosmic radiation in mountains, aeroplanes etc)
  • Radioactive subsoil (higher rates of thorium, uranium, etc.)
  • Medical equipment (in radiodiagnostic laboratories X-rays, CT scans etc.)
  • Cement, aluminum and phosphate fertilizers factories, oil drilling and coal burning power stations

So far there have been recorded more than 152 radioactive leakage incidents in nuclear plants, industrial plants, during nuclear tests etc. [UNSCEAR 2008 REPORT: VOLUME I, page 15]. In many cases of nuclear leaks and accidents, such as the Chernobyl accident, the public is informed too late, resulting in not enough time to take precautions. With a radioactivity meter can you see first every increase of radioactivity levels in your area!

What features to look for in a radiation meter

Manufacturer

A reputable company or country of manufacture could mean better quality and extended operating life. Being more geographically close might be helpful if there is a malfunction of the meter or you need to send it back for recalibration.

Average price

This is the average price of the meter sold by the various online sellers shown on the bottom of each table.

Types of radioactivity detected

Each meter detects a certain portion of the radioactive spectrum. None of them can detect everything.

The main radiation types are:

  • Alpha particles: particularly dangerous when ingested through eating or inhalation (radon) through the air. They can easily be shielded even with a piece of paper.
  • Beta particles (or electron radiation): dangerous especially when ingested through eating or inhalation through the air. They can be shielded with a metal foil (e.g. aluminum).
  • Gamma rays: electromagnetic radiation emitted during radioactive decay (along with alpha and beta radiation) - they have high penetration and can travel several meters in the air. They can be shielded with thick cement, lead, steel etc. They are a big part of terrestrial radiation.
  • X rays: very high frequency electromagnetic radiation generated when a strong electron beam bombards a metal inside a glass tube, which is generated mainly by artificial sources in medical diagnostics etc - they have high penetration and can travel several meters in the air. They can be shielded with thick cement, lead, steel etc.

Gamma rays (along with radon gas concentrations which are better measured by radon meters, digital alpha particle counters, radon detectors or dosimeters and not radiation, radioactivity or Geiger counters), are the most important for building biology assessments.

Some manufacturers also mention the energy resolution of the meter measured in kiloelectron (keV) or megaelectronvolt (MeV) = 1000keV = 1000000 eV. So beta radiation detection 0.25 –3.5 MeV means the meter can detect beta particles with energy from 0.25 up to 3.5 MeV.

Radiation detector type

There are various types of radiation detectors which use different technology to measure radiaoactivity.

  • Geiger-Müller Tube detectors: They use a gas filled tube with a high voltage wire which collects the ionization caused by radioactive radiation. This technology is used by the most common radioactivity detectors, called Geiger counters, which have low sensitivity and low cost. Geiger-Müller Tubes usually use detector windows with thin silicate sheets (Mica) which are relatively transparent to radiation (such as alpha particles) but impervious to most gases.
  • Scintillation Counters: They use crystals that generate light when they interact with radiation. They offer more accurate measurements but are pricey.
  • Other types: Silicon detectors, Neutron detectors, Semiconductor detectors etc.

Units of measurement

The active equivalent dose (in Sv-Sivert), measures the effect of radiation on the human body since it takes into account the type of activity (e.g., beta particles, gamma radiation, X, etc.) and the absorbtion by the human body. Other radiation dose unit used is the rem where 1 rem = 0,01 Sv or 1 Sv = 100 rem.

Most radioactivity meters record the effective dose rate of radioactivity, usually measured in μSv / h or uSv/h (micro sivert per hour) or mR/hr (milli rem per hour) = 1000μR/hr = 10μSv/h.

Some meters also measure CPM (counts per minute) which is the number of atoms in a given quantity of radioactive material that are detected to have decayed in one minute. Count rate measurements are normally associated with the detection of particles, such as alpha particles and beta particles.

Measurement range

We recommend the radiation detector can measure at least from 0.1 μSv / h = 10 μR/hr = 0,01 mR/hr (natural background radioactivity levels) up to 10 μSv/h = 1000μR/hr = 1mR/hr (recommended safety limit for occupational exposure levels).

Measuring up to 100 μSv/h = 10000μR/hr = 10mR/hr is not necessary, unless you need to measure very high levels of radiation.

What are safe levels of exposure to radiation?

Radiation dose rate

Normal radioactivity values in the environment are <0.3 mSv / h (eg 0.13 μSv/h is the world average exposure to natural sources of radiation - except for radon [UNSCEAR, the United Nations Scientific Committee on the Effects of Atomic Radiation, www.unscear.org/unscear/en/faq.html] and values greater than 0.4 μSv/h trigger radiation alarm in Finland).

The exposure limits set by the legislation are:

European safe level for occupationally exposed 10 μSv/h (20 μSv/year - 2000 working hours per year) [Radiation Protection Regulations, OG / w / 216 / 6.3.2001 (whole body exposure)]

Potential health effects depending on the dose rate radiation 

  • 100 μSv/h: increased chance of illness
  • 100 000 μSv/h: nausea, vomiting (radiation sickness)
  • 1,000,000 μSv/h: increased chance of cancer
  • 10,000,000 μSv/h: organ damage and death within hours

The US Nuclear Regulatory Commission (NRC) identifies as high radiation areas in nuclear power stations after a nuclear accident when we exceed 1000 μSv/h [Wikipedia, Orders of magnitude (radiation)].

Radiation dose

Multiplying the dose rate with the total exposure duration we can specify the total radiation dose for a time period.

According to the Scientific Committee of the United Nations on the Effects of Atomic Radiation (UNSCEAR), the effects of radioactivity on humans per radiation dose are as follows:

  • <10 mSv: There is no direct evidence for health effects
  • 10-1000 mSv: No direct impact, increased incidence of certain types of cancer in exposed populations at higher doses
  • 1000-10000 mSv: Nausea, vomiting (radiation sickness), probability of death, increased incidence of certain types of cancer in exposed populations
  • > 10000 mSv: Death

Examples of radiation dose rates:

  • 10-hour flight by plane: 0,03 mSv
  • Chest X-ray: 0,05 mSv
  • CT: 10 mSv
  • Radon (annual report): 0,2-10 mSv (average 1,26 mSv)
  • Subsoil (annual report): 0,3-1 mSv (average 0,48 mSv)
  • Food (annual report): 0,2-1 mSv (average 0,29 mSv)
  • Cosmic radiation (annual report): 0,3-1 mSv (average 0,39 mSv)
  • Total annual radiation exposure from the natural environment: 1-13 mSv (average 2,4 mSv)

Data logging

Some meters offer the possibility to store the measurements and then download through a PC. We personally think this feature is not important for most users.

Display

A digital display gives you more accurate readings and has a more modern and professional look. Analogue displays are rather outdated, but are usually cheaper and will also do the job.

Backlight display

Not a necessary feature but is helpful when measuring in dark areas or in houses with no working lights.

Audio signal

Having audio signal which increases volume according to the radiation value, is helpful for finding radiation.

Audio alarm

Audio alarm is helpful for finding radiation hotspots but not necessary when you have audio signal. Some meters also allow you to set the alarm threshold.

Accuracy

Higher accuracy is good but it is more important for professional users and not for amateurs. Also, manufacturers show their accuracy data in various ways, making it difficult to distinguish the ones with crappy accuracy.

Batteries and battery life

If you plan to use the meter a lot then you should definitely take into account the battery type and life of the batteries used, because changing batteries frequently could elevate the operating cost significantly. Some meters are rechargeable so you don’t have to purchase new batteries every little while.

Low battery indication

Warns you about low battery so it helps you not run out of batteries unexpectantly.

Auto power off

Helps you avoid battery loss when you accidentally forget the meter on.

Carrying case

A good quality plastic case is very helpful for professionals or for those who frequently measurements in various locations.

Calibration service

If you need to check that everything works well in the future you might consider sending it for calibration (or recalibration if the meter was originally calibrated). This is especially important for professional users. In that case you should choose a manufacturer that offers this service. Also it would be better if the manufacturer is geographically close to you.

Warranty

The longer the warranty the better, especially if the meter is expensive.

Seller

We try to we recommend reputable companies, with good customer service, that can ship the meters worldwide.

Being more geographically close might be helpful if there is a malfunction of the meter, so we usually recommend one seller from the USA and one from Europe.

Also, buying from an overseas company means there will be some extra shipping costs and possible tax charges in the customs office.

Finally, please be sure to check all the mentioned features (warranty, prices etc) also in the sellers page, because they could be different from those mentioned in the following comparison tables or have changed since the time this article was written.