Testing
Can a Geiger counter measure radon?
Short answer
Not as a radon level you can act on. A Geiger counter counts pulses of radiation and reads in counts per minute, while radon is measured as a concentration in air, in pCi/L, with a radon test kit or radon monitor, which is what EPA's guidance on radon is built around.
The instrument
What a Geiger counter measures
A Geiger counter is a radiation detection and measuring instrument built around a gas-filled tube with electrodes. When ionizing radiation passes through the tube, a pulse of current is counted, and the number of pulses per second measures the intensity of the radiation field. Geiger counters are the most commonly used portable radiation detectors: hand-held devices that detect the presence of radiation, often used in health physics, nuclear work and geology.
| Geiger counter | Radon test kit or radon monitor | |
|---|---|---|
| What it reports | Counts per second (CPS) or counts per minute (CPM) | A radon concentration in pCi/L |
| What it is for | Detecting the presence of radiation | Measuring radon levels in the home |
| Used in EPA's radon testing steps? | No | Yes: short-term and long-term radon tests |
What it reports
- Geiger counter
- Counts per second (CPS) or counts per minute (CPM)
- Radon test kit or radon monitor
- A radon concentration in pCi/L
What it is for
- Geiger counter
- Detecting the presence of radiation
- Radon test kit or radon monitor
- Measuring radon levels in the home
Used in EPA's radon testing steps?
- Geiger counter
- No
- Radon test kit or radon monitor
- Yes: short-term and long-term radon tests
The physics
Why it cannot give you a radon level
The units draw the line: radon levels are measured in picocuries per liter (pCi/L), and Geiger counter readings in counts per second or counts per minute. A count rate is not a concentration of radon in air, so it cannot be compared with EPA's action level of 4 pCi/L.
Radon also gives off the kind of radiation that is hardest to catch from outside. Radon emits alpha particles, which a thin layer of light material, such as a sheet of paper, can stop, and which cannot get through the outer, dead layer of skin. But if alpha-emitters are breathed in, the alpha particles can damage sensitive living tissue. That is why radon is a lung risk, and why it is measured in the air you breathe.
The right tool
What does measure radon
Radon test kits measure radon levels in the home. At-home kits are canisters, detectors or devices that you leave in place for a set period and then send to a laboratory for analysis, and professionals can also come to your home and measure the radon level.
What does measure radon
Short-term radon test
Stays in the home two to 90 days, depending on the device, then goes to a lab. The usual first test.
Short-term kitsLong-term radon test
Stays in the home more than 90 days, so it is more likely to show your year-round average.
Long-term kitsContinuous radon monitor
Runs on power and usually gives hourly readings and an average for the test period.
Radon monitorsProfessional radon test
A qualified radon tester, very often a home inspector, places the device and reports the result.
Find a tester
Not sure which? The test chooser picks one for your situation, and many states give kits away: see free and low-cost kits by state.
FAQ
Geiger counter and radon questions
Will a Geiger counter react near radon?
It may register radiation, but its reading is a count rate in counts per minute, not a radon concentration in pCi/L, so it cannot tell you your home's radon level or whether you are above EPA's 4 pCi/L action level.
Can I use a radiation detector instead of a radon test?
No. Use a radon test kit or a radon monitor, which report pCi/L. Testing is the only way to know whether you and your family are at risk from radon.
What unit is radon measured in?
In the U.S., picocuries per liter of air (pCi/L). Many other countries, and many monitors, use becquerels per cubic meter (Bq/m3); EPA's action level of 4 pCi/L is 148 Bq/m3. A Geiger counter's counts per minute is a count rate, not a concentration, so it is in neither unit.
Is radon radioactive?
Yes. Radon is an odorless, colorless, radioactive gas. See is radon radioactive.