You've been monitoring your radon levels for a while, but what do these numbers mean?
Should you be worried?
Is it necessary to install a radon pump?
Should you just open the window more often?
Let's clarify a couple things first:
We recommend you measure in one location for at least 30 days, to understand the behavior of radon in your environment and to obtain enough data.
The longer you measure for in one location, the more accurate your readings will be. You should always consider your long term average when deciding to pursue radon mitigation action.
Radon levels fluctuate naturally. If you see an irregularly high reading of radon one day, it is generally nothing to be alarmed by. However, if after some weeks of monitoring you see consistently elevated radon levels, you'll want to keep a close eye on how they continue to evolve.
When to contact a radon professional
The chart below offers guidelines on radon levels (in both picocuries and becquerels for imperial/metric measurement system) and what action to take in response:
Radon monitors can also be used to evaluate the effectiveness of mitigation systems, ensuring that radon levels are reduced to safe limits.
Why is ventilation and sealing cracks effective?
Sub-Slab Depressurization Method
One of the most effective ways to reduce radon levels in your home is through sub-slab depressurization. This method involves installing underground piping beneath the foundation of your home and using an exterior exhaust fan to draw radon gas from beneath the foundation and vent it outside before it enters your living space. This approach can also be adapted for homes with crawl spaces. Additionally, sealing cracks and openings in floors and walls can complement the effectiveness of the system.
Radon exists everywhere, even in the open sea, but radiation only becomes a problem when it starts concentrating. It is easier for radon to accumulate in well-insulated office buildings or homes than in areas that are open or constantly ventilated.
Radon particles have a half-life of 3.8 days. This means it’s possible to reduce concentration with proper ventilation alone. As ventilation increases, radon concentration will decrease.
In areas where there’s constant ventilation, radon levels will tend to align with normal concentrations outdoors. Try to ventilate and measure for at least a week in a particular room to see if levels get closer to normal outdoor values (~10 Bq/m3).
While it is recommended to implement mitigation measures in rooms where levels are much higher than the reference levels, values slightly above average are not as harmful if you spend a little time in there. In other words, if you have a room with an average radon concentration of 350 Bq/m3 but only use the room for storage or pop in once in a while, you will be safe. However, you should always make sure the radon is not seeping into other areas of the building. You can find more information here from a case study about radon toxicity.
What if I still have high readings after experimenting with ventilation and sealing cracks?
Advanced Mitigation Option: External Fan Installation
Installing an external fan for radon extraction is a common advanced mitigation method. This involves assessing your home's construction, installing piping beneath the foundation or in crawl spaces, and positioning an exterior exhaust fan to vent radon gas safely away from living areas. Sealing cracks and gaps in floors and walls further enhances the system's effectiveness.
Have you measured for long enough since you tried lowering your radon levels?
If you have tried to ventilate and seal cracks, you should continue to measure again for several weeks (ideally at least 30 days), to see the effects of the mitigation.
If you are genuinely still seeing high levels of radon after this, it's time to consider contacting a radon professional.
Sub-slab depressurization is one such professional solution that can effectively reduce radon levels in your home.
Contact a radon professional if you see:
Moderately high levels for longer than 3 months
100 - 149 bq/m3
2.7 - 4 pci/lVery high levels for 1 month
150+ bq/m3
4.1+ pci/l
Further Information
According to the World Health Organization (WHO) on its 2009 Handbook on Indoor Radon, there are over 40 case-control studies that have contributed to understanding the link between radon exposure indoors and lung cancer. These studies have also helped to establish what normal levels of radiation are or, more accurately, those considered acceptable.
Radon is leading cause of lung cancer among non-smokers. Each country or region is in charge of developing a national plan for mitigation and control of radon gas; these plans are “aimed at minimizing exposure of the population to radon”. The European Union has established some guidelines that take into account the soil conditions.
There are factors that affect indoor radon levels, like weather conditions in your area or the time of the year. In zones far from the equator, there are normally higher levels during the winter than the summer because in the cold weather most people ventilate less.
The Radon and Health Fact sheet from the WHO states that:
“Radon levels in existing homes can be reduced by increasing under-floor ventilation, installing a radon sump system in the basement or under a solid floor, avoiding the passage of radon from the basement into living rooms, sealing floors and walls, and improving the ventilation of the house. Passive systems of mitigation have been shown to be capable of reducing indoor radon levels by more than 50%. When radon ventilation fans are added radon levels can even be reduced further.”
National agencies normally recommend the most cost-efficient methods to reduce radon, should levels not be reduced by simple ventilation. If the problem is severe, many countries offer financial support or tax credits to help homeowners with the installation of active mitigation methods.
There is usually a list of certified radon professionals in each country that can help you reduce the concentration of radon. Many national agencies provide this directorate or point you in the right direction to find the person or business who can help you. Search for “radon” on your government website, otherwise turn to the local Health and Safety authorities for more information and help.