What do radon levels mean? A guide to understanding radon readings

 

Did you recently get your radon test results back and are wondering what the numbers mean?

This guide explains exactly what your radon level reading means for your health, whether you need to take action, and what steps to take next.

TLDR: The EPA recommends taking action if your radon level is 4 pCi/L (148 Bq/m³) or higher, with Health Canada recommending action if levels are at or above 200Bq/m³.

The World Health Organization sets a more conservative threshold of 2.7 pCi/L (100 Bq/m³).

Remember: Any radon exposure carries some lung cancer risk, but levels below 4 pCi/L (148 Bq/m³) are generally considered manageable.

 

How to interpret radon readings

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 recommended.

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) for more than 1 month are deemed high and demand immediate action. In such cases, homeowners should promptly seek professional radon mitigation to address the radon problem.

Why do radon levels change?

Like most gases, 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, so it's 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 that allows air samples to flow into it. Inside this chamber, there is a photodiode that 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 radon levels can fluctuate 

• Your home's foundation and insulation

• Snowfall, ice, rain, earthquakes 

• Temperature, humidity, and air pressure

• The ventilation in your home

Below we dig a little more into exactly why these levels change over time. 

Why do radon levels fluctuate?

If you're monitoring radon with a digital detector, you've probably noticed that your readings change - sometimes dramatically - from hour to hour and day to day. This is completely normal. Understanding why radon levels fluctuate helps you interpret your readings correctly.

Short-term radon fluctuations

Your radon level can double or halve within hours due to:

Weather and atmospheric pressure:

- Falling barometric pressure (before storms) draws more radon into your home
- Rising pressure (sunny, clear days) reduces radon infiltration
- Radon often spikes 12-24 hours before storms

Temperature differences:

- Cold outdoor temperatures create stronger "stack effect" (warm air rising, pulling radon up from soil)
- Hot summer days reduce pressure differentials and radon entry
- This is why winter radon levels are typically 2-3x higher than summer levels

Wind conditions:

- Strong winds create pressure variations around your foundation
- Wind direction affects which side of your home has lower pressure
- Gusty weather can cause rapid radon level swings

Home ventilation:

- Opening windows drops radon levels within 1-2 hours
- Running exhaust fans pulls air (including radon) from soil
- HVAC operation affects air pressure and radon entry
- Closing up the house for winter causes levels to rise

Seasonal radon fluctuations:

Radon levels follow predictable seasonal patterns:

Winter (December-February): HIGHEST LEVELS
- Homes sealed tight against cold
- Windows and doors closed for months
- Heating systems create negative pressure
- Snow cover prevents radon from escaping soil surface


Spring/Fall (Transition seasons): MODERATE LEVELS

- Partial ventilation as weather warms/cools
- Intermittent window opening

Summer (June-August): LOWEST LEVELS (traditionally)

- Frequent window opening
- Air conditioning creates different pressure dynamics
- Warmer soil allows more radon escape outdoors

In short, every home will have some level of radon, but readings will be higher in the colder months.  This is why the EPA recommends testing during the heating season (October-April), as winter tests will reveal your worst-case exposure. If your winter test is below 4 pCi/L, you can be confident your year-round average is safe.

Long-term radon changes (month-to-month)

Beyond daily and seasonal variations, radon levels can change over months or years due to:

Foundation settling:
- New cracks develop as homes age
- Existing cracks widen from ground movement
- Basement waterproofing can redirect radon entry points

Landscaping and drainage changes:
- New landscaping that alters water flow
- Downspout or drainage modifications
- Soil erosion or settlement near foundation

Home renovations:
- Basement finishing alters air pressure and ventilation
- New HVAC systems change pressure dynamics
- Foundation repairs may seal some cracks but open others

Soil moisture variations:
- Drought conditions allow more radon release from dry soil
- Heavy rainfall temporarily suppresses radon (water fills soil pores)
- Long-term moisture patterns shift over years

Nearby construction or geological events:
- Construction vibrations can create new foundation cracks
- Nearby excavation changes soil pressure patterns
- Earthquakes (even minor ones) can alter foundation integrity

What this means for monitoring

Focus on averages, not spikes:
Digital radon monitors show hour-to-hour fluctuations, but these momentary spikes aren't cause for alarm. What matters is your 7-day, 30-day, and annual average readings.

Test for at least 30 days:
Short-term tests (48 hours) can miss important patterns. Allow your radon detector to measure for at least one full month to capture normal fluctuations and get a reliable average.

Retest annually:
Because long-term changes can occur, retest your home once per year, preferably during winter when levels are highest. This ensures you catch any increases before they become health hazards.

Monitor after changes:
Whenever you make significant changes to your home (renovations, HVAC upgrades, foundation repairs), retest for 30 days to see how radon levels are affected.

Understanding Airthings readings

If you're using an Airthings digital radon detector, the device provides multiple timeframes:
- Current/24-hour reading: Shows recent fluctuations; useful for seeing immediate impacts of ventilation
- 7-day average: First reliable indicator of your home's typical level
- Long-term average: Most important number for health risk assessment

Even better: monitor over a year to understand your home's average annual radon exposure. 

Don't panic if your 24-hour reading occasionally spikes above 4 pCi/L. Look at your 7-day and long-term averages to determine if action is truly needed. The color-coded indicators (green, yellow, red) are based on these longer-term averages, not momentary spikes.

The radon insights feature in our app will help guide you through your radon levels and what you need to do about them.

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. 

FAQ

How does radon enter homes, and where does it come from?

Radon originates from the decay of radium in the soil and can enter homes through cracks in the foundation, gaps in walls, floors, or even through well water. Understanding its source is essential for effective mitigation.

What are the common symptoms or health risks associated with radon exposure?

Radon exposure is primarily linked to lung cancer. Common symptoms of radon exposure are often silent, but the long-term health risks are substantial. Early detection and action are crucial.

What should be done when the radon monitor shows> 150 Bq/m3 or > 4.0 pCi/L? 

1. Confirm the accuracy of the readings by monitoring the average for 1 month.
2. If the levels remain the same or increase, continue monitoring. Otherwise, continue monitoring to ensure you stay at safe levels.
3. Inform occupants about the elevated levels and associated health risks.
4. Contact a radon mitigation professional for assessment and appropriate action.
5. Mitigate the issue based on their recommendations.
6. Retest after mitigation to ensure safe levels.
7. Regularly monitor radon levels to maintain safety.

How can I test my home for radon, and is professional testing necessary?

Homeowners can use radon testing kits or digital radon detectors for initial testing. Professional radon testing services are available and recommended for a comprehensive assessment, especially if the radon level exceeds > 150 Bq/m3  or > 4.0 pCi/L for a period of more than 1 month.

What are acceptable radon levels in a home, and why is it important to know them?

Acceptable radon levels, defined by governmental or health organizations, vary by region. Knowing these levels ensures indoor air quality is safe. Elevated radon levels increase lung cancer risk. Levels from 0 to 2.6 pCi/L (0-100 Bq/m3) are acceptable. While intervention isn't urgent, regular monitoring is wise. Homeowners can improve ventilation and seal foundation cracks preventively.

How much can radon levels fluctuate over time, and what factors contribute to these fluctuations?

Radon levels can fluctuate daily and are influenced by factors such as weather conditions, ventilation, soil composition, and even geological events like earthquakes. Understanding these fluctuations is important for continuous monitoring and taking timely action if levels rise.

What is considered a safe radon level, and why should homeowners aim for this level in their homes?

A safe radon level is typically defined as one that poses a minimal health risk, such as levels below <150 Bq/m3  or < 4.0 pCi/L - the recommended threshold set by health organizations. Homeowners should aim for safe levels to reduce the risk of radon-related health issues, primarily lung cancer, and ensure a healthy living environment.

Are there DIY methods to reduce radon levels, or should I always hire a professional?

While some DIY methods, like sealing cracks or improving ventilation, can help reduce radon levels, hiring a professional radon mitigator is often the most effective and safest solution for high radon levels.

Is radon exposure a concern in all regions, or are certain areas more at risk than others?

Radon levels can vary significantly by geographical region. Some areas have higher natural radon concentrations in the soil, making them more prone to elevated indoor radon levels. Local awareness is essential. Check out radon levels around you at radonmap.com

Are there government regulations or incentives for radon testing and mitigation?

Some governments or regions may have regulations or incentives related to radon testing and mitigation. It's essential to check with local authorities or organizations for any available programs or requirements.