Radon levels: What do they mean?



July 18, 2023


Airthings most frequently asked question? "What do my radon levels mean?" Below we explain everything you need to know about your levels. Arm yourself with the information you need to make small changes to your home, improve your radon levels, and your health!

What is radon gas, and how is it measured?

Radon, an invisible, odorless, and potentially harmful radioactive gas, is a significant concern for homeowners due to its scientific link to lung cancer

Radon exposure is typically quantified in becquerels per cubic meter (Bq/m³). However, in the United States, the commonly used unit of measurement is picocuries per liter (pCi/L). It is essential to acknowledge that radon gas exposure can differ from one geographical region to another, and it is crucial to adhere to local recommendations, often provided by authoritative bodies like the World Health Organization (WHO) and EPA (United States Environmental Protection Agency).

Radon gas is generated by the radioactive decay of radium, an element that was originally discovered in 1898 by Pierre Curie, Marie Skłodowska Curie, and G. Bemont. Radioactive elements are unstable, always in a constant struggle to decide whether to hold onto all of their atomic energy in the nucleus or release some of it. That "decay" of the nucleus releases radiation.

One curie is equal to the radioactivity of one gram of radium, which decays at 2.2 trillion disintegrations per minute3. Sounds fast, doesn't it? It also sounds small, right? Read on.

Why it is important to control healthy indoor radon levels?

Measuring radon exposure at home or building is key to protecting the health of anyone breathing the air, but interpreting those levels is not quite as exact without radon tests and monitoring. As they say, everything is relative, and what is an acceptable radon gas level to one country or organization may differ from what is acceptable to another. This is influenced by numerous factors including the type of rocks and soil beneath a building, ventilation, and duration of time spent in the building.

Radon - dangerous, invisible, in every home

One thing remains certain: radon exposure can cause lung cancer. According to EPA estimates approximately 21,000 people die from radon-related lung cancer every year in the United States and 20,000 in the EU.

That alone should be the reason to find out if you, or your family, are being exposed to excessive levels of the dangerous gas. Radon gas levels in the home need to be monitored daily as the levels fluctuate over time to reduce health risks. Radon can build up in the air in any home or building whether it has a basement, is sealed or drafty, or is new or old. There is no known safe level of radon and you should always aim to have the lowest level.

The World Health Organization (WHO) recommends that countries adopt reference levels for safe levels of the gas of 100 Bq/m3 (Becquerel per cubic meter). If this level cannot be implemented under the prevailing country-specific conditions, WHO recommends that the reference level should not exceed 300 Bq/m3.

How to read radon level chart?

Airthings View Plus, View Radon, Wave Radon, and Wave Plus have color-coded visual indicators. This makes it easy to get an overview of the air in your home. In addition, you can check in the Airthings app if the radon sensor is good (green), fair (amber), or poor (red).

Airthings app chart on radon levels in pCi/L and Bq/m3

Radon levels chart from Airthings

What is the difference between pCi/L and Bq/m3?

Picocuries per litre of air, or pCi/L: is one of the preferred measurements for the speed of decay in radon, is equal to one trillionth of a curie, abbreviated as pCi. The pCi unit is used in the United States because it is required by federal law. Just about everywhere else that uses the metric system, including the WHO, measures in Becquerels. 1 pCi/L is equal to 37 Bq/m3.

The Becquerel unit, abbreviated Bq/m3: is named after the scientist Henri Becquerel. The preferred radon level measurement unit is Becquerels per cubic meter, Bq/m3. One Becquerel equals one radioactive disintegration per second.

How to Interpret results of the radon test


Safety level

Radon Level in Bq/m3

Radon Level in pCi/L

Actions to take based on  radon readings


Safe radon levels < 50 Bq/m3 0 - 1.3 pCi/L Radon levels are extremely low, and no immediate health risks are associated. Consider periodic retesting.



50 - 100 Bq/m3 1.3 - 2.7 pCi/L Radon levels are within recommended limits. Regular testing is still advisable to ensure they remain low.



Acceptable radon levels 100 - 150 Bq/m3 2.7 - 4.0 pCi/L

Radon levels are approaching the recommended limit. Continuous monitoring and further investigation are advisable.

Check out our radon reduction tips.

Poor Dangerous radon levels > 150 Bq/m3 > 4.0 pCi/L

Radon levels are above recommended limits, potentially hazardous. Immediate action is necessary to reduce radon exposure. 

Learn more about radon mitigation.


To grasp the significance of radon gas levels, let's dissect the interpretations of radon readings:

  1. Minimal Levels (Up to 1.3 pCi/L or 50 Bq/m3): concentrations below 1.3 pCi/L are considered safe radon levels, necessitating no immediate action. Nonetheless, continuous monitoring is prudent.

  2. Low Levels (1.3 to 2.6 pCi/L or 50  to 100 Bq/m3): levels falling within this range are classified as acceptable radon levels. While immediate intervention is not imperative, regular monitoring is advisable. Additionally, homeowners can experiment with ventilation and sealing foundation cracks as a preventive measure.

  3. Moderately High Levels (2.7 to 4 pCi/L, or 100-150 Bq/m3): levels between 2.7 and 4 pCi/L are considered moderately high, warranting attention. Initial steps may involve enhancing ventilation and monitoring the situation. If no improvement is observed after three months, it is advisable to consult a professional radon mitigator.

  4. Risk Levels (Above 4 pCi/L or 150 Bq/m3 and up): levels exceeding 4 pCi/L (150 Bq/m3) are deemed high, demanding immediate action. In such cases, homeowners should promptly seek for professional radon mitigation to address the radon problem.

Why do radon levels change?

Like most gasses, radon concentration fluctuates daily. The amount of radon gas emitted from the ground and the amount of radon gas particles entering that actually enter our home can and how much radon can change for many reasons. It can be affected by natural sources such as cold weather, wind, pressure, and shifting soil - even earthquakes and local construction.

The radon gas concentration within our homes is often much greater than outside. This is because the gas comes from the ground and is captured and contained in our homes, resulting in levels that we seldom find in nature. Radon concentration changes over time, that’s why it's so important to measure continuously, so you can be alerted to high levels and take simple steps to improve them. 

Expert sensors, such as Airthings patented radon sensors use alpha spectrometry developed in-house by our CERN scientists. The radon sensor consists of a passive diffusion chamber, which allows air samples to flow into it. There is a photodiode located inside this chamber, which essentially counts the amount of "daughter" radon gas particles in the air sample. This makes long-term monitoring effective and reliable. 

External factors affecting how much can radon levels fluctuate 

  • Your home's foundation and insulation

  • Snowfall, ice, rain, earthquakes 

  • Temperature, humidity, and air pressure

  • The ventilation in your home

What are acceptable radon levels?

The best radon level measurement would be zero. However, maintaining your radon levels bellow 2.6 pCi/L or 100 Bq/m3 is the safest level. Unfortunately, keeping radon at zero level is not possible. The average global outdoor radon concentration varies between 5-15 Bq/m3, equal to 0.135-0.405 pCi/L.

For every 99.9 Bq/m3, or every 2.7 pCI/L increase in long-term radon exposure, lung cancer risk rises 16%. The thing to remember is that the lower the level, the lower the risk. As radon gas can accumulate indoors, it is important to monitor daily. Airthings radon detectors can give you peace of mind so that you can take action because you are notified when high radon levels occur. 

Depending on the country, acceptable radon levels vary. A generally accepted action for the level of radon in the air, established by the World Health Organization, is 100 Bq/m3, or 2.7 pCi/L. Homes or structures measuring high radon levels are advised to take remedial action to lower radon levels. The WHO further advises an upper limit that should not be exceeded at 300 Bq/m3, or 8 pCi/L.

In the United States, the Environmental Protection Agency action level of 4 pCi/L is the standard, a little higher than that of the WHO. It is also thought that reducing levels of exposure to radon to sub-4.0 p/Ci would cut yearly cancer deaths from exposure to radon in half, saving over 10,000 lives in the U.S. alone. 

How to properly monitor radon levels and identify the radon problem?

To effectively manage radon levels, the use of a digital radon detector is recommended. This device enables homeowners to monitor radon levels on a daily basis, facilitating the early detection of any alarming trends or fluctuations that may require further action. Maintaining low radon levels is essential for ensuring a safe and healthy living environment.

Here are effective measures to consider:

  • Improve Insulation: Enhance the insulation in your home to prevent radon infiltration.

  • Seal Foundation Cracks: Identify and seal any existing cracks in your home's foundation to reduce the risk of radon ingress.

  • Mitigation System Installation: In cases of persistently high radon levels, installing a radon mitigation system is often the most effective solution.

Why does radon sensor sampling affect my radon levels?

Radon will not be distributed evenly around a room so the way it's measured has to accommodate that. 

Imagine adding a dash of cream to a cup of black coffee but not stirring it. If you then take multiple samples from a small spot of that coffee to test for the level of cream, you would get very different readings over time as the cream slowly blends in with the coffee. Radon sampling works in the same way.

As a result, Airthings radon sensors give a short-term sample reading as well as an average long-term reading. This is why we recommend allowing your radon detector to measure for at least 30 days so that the monitor can obtain enough air samples to provide a reliable long-term, average radon level.

How to fix high levels of radon?

High radon levels can be fixed easily and simply. Whether it is following easy radon reduction tips, increasing ventilation, performing DIY fixes, or contacting a radon mitigator, radon gas levels can be improved dramatically. The first step is to monitor for radon so that you can be alerted to risk levels and make small changes where and when necessary. 




Radon map

Thousands of Radon sensors across the world, broken down by location. See your region's approximate risk level.


Thousands of Radon sensors across the world, broken down by location. See your region's approximate risk level.