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Welcome to the Radon Learning Hub! Explore articles covering everything you need to know about radon—from its origins and the basics of radiation to practical guides on measuring radon levels and understanding their impact on health. Whether you're a homeowner, contractor, or simply curious, our articles are here to empower you with knowledge for a safer, healthier environment.
What is Radon, and Why is it Dangerous?
Basics of Radiation
The earth is composed of elements like iron, nickel, and sulfur. There are 92 naturally occurring elements, and all of them are made up of atoms. An atom contains a nucleus, made up of protons and neutrons bound together, and electrons that orbit the nucleus. Neutrons have a neutral electric charge, while protons are positive and electrons are negative. An element is considered stable if its atoms have a neutral charge, meaning that the positive charge of the protons and the negative charge of the electrons cancel each other out.
Some elements, such as polonium, uranium, and radon, are unstable. Atoms of these elements have unequal numbers of protons and electrons, leading to instability. These elements will eventually go through decay, shedding some of their neutrons or protons. If the element loses only neutrons, it may become an isotope of the same element; if it loses protons as well, it may transform into a completely different element.
What matters to us is that this shedding of parts of the atom releases energy as a byproduct. This emitted energy, which moves through space, is called radiation. Elements going through decay can emit different types of radiation: alpha, beta, or gamma.
For example, nuclear reactors primarily emit beta and gamma radiation. Beta radiation can be contained by relatively thin sheets of metal, plastic, glass, and even water. However, gamma radiation can pass through these materials, so thick layers of concrete or lead are used to contain it. Alpha radiation, on the other hand, is the least penetrable. It can be stopped by a sheet of paper or even the surface of our skin.
In short, some elements with unstable atoms go through decay, emitting different types of radiation—alpha, beta, or gamma—as they attempt to reach a stable state. Importantly, the amount of radiation matters. Think of the difference between the small amount of gamma radiation during a dental X-ray versus the high levels of gamma radiation from a nuclear reactor.
How Radon Gets into Buildings?
Radon gas originates from Uranium-238. Because uranium atoms are unstable, they decay into thorium-234, emitting alpha radiation. Thorium-234 then decays further into other elements, and so on, through a sequence of seven elements, before it eventually becomes radon gas (Radon-222). Radon gas is also unstable and continues to decay until it eventually becomes Lead-206, a stable element.
You might ask why we’re specifically concerned about radon and not the other elements in the decay chain. Uranium and these other elements are located in the earth’s crust and soil, which generally keep them trapped underground. As long as this decay and radiation happen beneath the surface, away from our homes, it poses little danger. However, Radon-222, being a gas, can escape into the air. Like any other gas, radon is lighter than air and rises upward.
Radon gas escapes the soil and accumulates under concrete slabs, reaching high concentrations. It then seeps into our homes through cracks, drains, sump pumps, and other openings. In some cases, radon gas enters homes more freely through crawl spaces with minimal covering, such as gravel or exposed soil, or through unfinished floors in older homes. A building is like a boat in water; small cracks let water seep in slowly, while larger openings allow it to rush in. Similarly, radon gas enters more quickly through bigger entry points. Unfortunately, even concrete is porous over time, allowing gases to pass through.
The concentration of radon gas in a house depends on several factors, such as the amount of radon in the soil, air movement within the building, temperature differences, pressure in the soil, and soil porosity. For instance, radon naturally moves to areas with lower concentrations, a process called diffusion. Air movement caused by kitchen fans, bathroom exhaust fans, and dryers can draw radon gas into buildings. Temperature differences, such as open windows or heating, increase air movement, making it easier for radon to flow. Pressure changes in the soil due to rain or wind, and differences in soil porosity (e.g., gravel versus clay), also affect how much radon gas enters a building.
To summarize, elements that decay into radon gas are found everywhere in the soil. Even outdoor air contains tiny concentrations of radon. The level of radon gas in a building will vary depending on soil conditions, location, and other environmental factors.
What Does Radon Do to Our Health?
Now that we understand how radon forms and travels into buildings, let’s examine how it affects our health.
We know how gamma radiation works from experiences like medical X-rays. When we get an X-ray, gamma rays travel through our tissues to produce an internal image, which only concrete or lead can fully block. That’s why we wear protective covers during X-rays to limit radiation exposure to other parts of the body.
Beta and alpha particles, meanwhile, are larger and do not penetrate deeply, as they are typically stopped by skin. However, the real danger comes from inhaling or swallowing these particles. When indoor air contains high concentrations of radon gas, we breathe it in. Inside our lungs, radon gas continues to decay, releasing alpha particles directly within the human body. For example, when Radon-222 decays into polonium-218, it emits alpha radiation. Alpha particles are then released from the decaying atom’s nucleus, hitting the surrounding lung cells. Since alpha particles cannot penetrate deeply, they impact only the nearby cells, including the DNA within those cells, which can lead to damage.
Each radon decay releases alpha or beta particles, each posing a risk to human cells. Over time, this can prevent lung cells from dividing normally, eventually leading to cell death. Cells can repair some damage, but with continued exposure, the repair mechanisms may be overwhelmed, and mutated cells may continue to divide abnormally, potentially leading to lung cancer. Although radon exposure does not guarantee lung cancer, it significantly increases the risk, much like cigarette smoke.
Radon, along with tobacco smoke, benzene, and asbestos, is classified as a Group A carcinogen. It poses a greater risk and causes more harm in high concentrations but is still harmful in lower amounts over prolonged periods. Radon’s health effects are cumulative; lower doses over long periods can be as dangerous as higher doses over shorter periods. In the United States, radon exposure is responsible for approximately 21,000 deaths annually—more than those caused by drowning, fires, toxic waste, or pesticides, and even more than deaths from drunk driving (17,400) or carbon monoxide poisoning (400).
To summarize, radon gas becomes a health risk when inhaled because it continues to decay inside our lungs. This decay releases radiation particles that can damage cellular DNA. The longer and more intense the exposure, the greater the damage, increasing the chances of cellular mutation and cancer. Just like with smoking, the duration, concentration, and frequency of radon exposure matter. Living in a high-radon environment over a long period presents a significant health risk.
Closing Thoughts
Understanding how radon forms, travels into buildings, and impacts health highlights the importance of testing and mitigation. Like other environmental hazards, increased awareness and proactive measures can significantly reduce the risks radon poses to our health.
How is Radon measured?
How is Radon measured?
What is pCi?
What is pCi?
Radioactivity is a property of certain materials to emit energy in the form of radiation. This phenomenon occurs due to instability in atomic nuclei, caused by an imbalance of neutrons. When an unstable nucleus releases particles and energy to reach stability, the process is known as radioactivity. In the United States, radioactivity is commonly measured in curies (Ci), while other regions, such as Canada and Europe, use the unit becquerels (Bq).
The term "curie" is named after the renowned scientist Marie Curie, a Polish-French physicist and chemist who conducted groundbreaking research on radioactivity. Curie became the first woman to win a Nobel Prize and, notably, the first person to receive it twice. Her second Nobel Prize, in Chemistry, honored her discovery of the elements polonium and radium. Curie chose the name “polonium” to reflect her Polish heritage.
In 1902, Curie successfully isolated 100 milligrams of nearly pure radium chloride from uranium, observing that one gram of radium decayed at a rate of 3.7 x 10¹⁰ disintegrations per second. This rate of decay became known as a "curie" (Ci), and the term has since become an international standard for measuring radioactive decay.
In the United States, radon gas concentrations are measured in picocuries (pCi)—one trillionth of a curie, or 0.037 decays per second—within a liter of air, resulting in the standard measurement unit picocuries per liter (pCi/L). To simplify, 1 pCi/L of radon gas indicates 0.037 alpha decays per second, or about 2.22 decays per minute, in a liter of air. A resting person inhales approximately 7 liters of air per minute, so over time, exposure to elevated radon levels can result in significant, life-threatening alpha decay exposure.
In 1915, Curie produced hollow needles containing a colorless, radioactive gas given off by radium, later identified as radon, which was used for sterilising infected tissue during World War I. Tragically, her extensive exposure to radiation during her career likely contributed to her death in 1934 from aplastic anemia, a condition in which bone marrow fails to produce adequate blood cells.
Testing options: DIY vs Professional
Testing options: DIY vs Professional
Now that we understand the units for measuring radon, let’s look at how to measure it. There are several options, ranging from DIY kits to professional services.
DIY Radon Testing Kits
Home improvement stores sell DIY radon test kits, which include a charcoal-based detection packet. This packet should be placed in the testing area for 2–4 days, then mailed to a laboratory for analysis. Once the lab receives the kit, you can typically expect results within seven business days. Additionally, many state health departments offer free test kits upon request, though this option may take an extra week due to mailing time.
Accurate placement of the test kit is crucial. Factors like distance from doors and windows, the level of the house, the room size, and even height from the floor can impact results. House conditions, including open windows, HVAC settings, ventilation type, humidity, dust, and dryer use, also affect accuracy. To ensure reliable results, some people opt for professional radon measurement services.
Professional Radon Testing
Professional radon measurement specialists use calibrated equipment, suited to the building's specifics, and follow protocols to ensure precision. A common device for professional testing is the continuous radon monitor, which is certified for radon use and recalibrated annually. Professionals regularly perform duplicate and blank testing to keep results within acceptable error margins, with all tests documented for state health department records. Continuous monitors are compact (about the size of a shoebox) and battery-operated. They’re typically placed on a tripod or small table and left undisturbed throughout the test. Many of these devices are tamper-resistant, alerting technicians if moved.
The advantage of continuous monitoring devices is their ability to take hourly readings, often over a two-day period, capturing fluctuations and providing 48 data points. This data shows both the highest and lowest concentrations during the test, giving an average picocuries per liter (pCi/L) reading—essential for deciding if radon mitigation is needed.
Professionals may also use passive devices, which rely on different technologies such as static electricity discharge (electret ion chambers), alpha decay counting (alpha track detectors), and charcoal absorption (charcoal canisters, liquid scintillation devices). Unlike continuous monitors, passive devices are sent to a lab for analysis. While passive devices deliver reliable results, they provide only an average concentration over the testing period. In some cases, continuous data from active monitors may help professionals better assess radon entry patterns in a building.
Both DIY kits and professional radon testing services can indicate whether radon mitigation is necessary. Professional testing provides more detail and confidence, but regardless of the method, it’s essential to retest buildings every few years, as radon levels in soil can fluctuate over time.
Long term VS Short Term testing
Long term VS Short Term testing
Short-Term Tests
Short-term radon tests, which last from 2 to 90 days, are typically used for an initial assessment of radon levels in homes, businesses, or schools. These tests are useful for quickly determining if radon concentrations are high enough to require further action. Short-term tests are also commonly used as confirmatory tests when results are needed urgently, as in real estate transactions.
It’s recommended to avoid short-term tests during extreme weather, such as high winds or heavy rain, as these can temporarily alter radon levels. High winds create positive pressure in the soil on the windward side of the building, pushing radon gases up and into the structure. Similarly, rain increases soil pressure and groundwater levels around the building, driving radon gas toward lower-pressure areas indoors. For this reason, measurement professionals take weather conditions into account during testing and may recommend a retest if weather interfered.
Short-term tests also require closed-building conditions. This means keeping all doors and windows shut, except for regular entry and exit, for at least 12 hours before and throughout the test. Fans, such as those in windows or attics, should be turned off, and HVAC systems should be set to normal operating levels. Kitchen fans and laundry dryers should be used sparingly, as they can disrupt air pressure and alter radon levels.
Long-Term Tests
Long-term radon tests, lasting over 90 days, provide a more comprehensive view of radon levels. These tests are typically conducted to confirm high radon levels found during initial short-term testing or to determine an annual average radon concentration. Long-term testing captures radon level fluctuations that occur with daily and seasonal changes.
Indoor and outdoor temperature differences affect radon entry into a building. When indoor air is warmer, it rises and escapes, creating a “stack effect” that draws radon gas from the soil into the structure. As a result, radon concentrations can increase at night and during colder months, when indoor heating enhances this effect. Long-term tests account for these natural fluctuations, offering a more reliable measure of average radon exposure.
Closing Thoughts
Closing Thoughts
Understanding radon and its measurement can play a critical role in protecting health and safety in homes and businesses. With radon being a naturally occurring but potentially dangerous gas, regular testing is essential to monitor and manage its levels over time. DIY kits offer a cost-effective way to get started, while professional testing ensures thorough, accurate results—especially when long-term peace of mind is the goal. Whether using short-term or long-term tests, retesting every few years remains crucial as radon levels in the soil change over time. Taking these steps helps reduce radon exposure risks and ensures that indoor environments remain safe and healthy.
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