17Nov / 2015
Where radon occurs
Radon is a naturally-occurring radioactive gas produced by uranium decaying underground. It seeps into buildings through floors, walls in contact with soil, and through water or gas supplies. When inhaled, radon atoms decaying in our lungs can cause damage to cells and cause lung cancer.
It’s associated with geological types like granite and shale, and the probability of finding high radon levels has been mapped for the UK in the ‘Indicative Radon Atlas.’ Although detailed, it only gives an indication – you have to test to be sure.
How to test for radon
The most common test is a passive ‘track etch’ detector. These are placed in high-occupancy rooms during winter months, when levels are normally highest, and typically track over 90 days. This gives a time-averaged reading over a long exposure, where variables such as weather, geology, building use, heating and ventilation can be taken into account: interpretation of results is crucial.
High radon levels indoors can be described as an engineering fault. Employers have a legal duty to protect employees from concentrations above 400 Becquerels (Bq) per cubic metre. There is no legal duty to reduce levels in the home, but an action level of 200 Bq m3 is recommended.
If a workplace is in an area known to be affected by radon, testing is a legal requirement. However, it’s also advised if you are near an affected area, or wish to pursue a precautionary approach. The radon atlas is only indicative; some areas may be affected which will not appear on the map.
Retrofitting radon reduction measures
If high levels are found, it’s possible to retrofit radon reduction measures like radon sumps. These are excavated areas below the building, fitted with exhausts leading outside. Electric fans create negative pressure in the sump, attracting radon gas and allowing it to be expelled. Such installations require professional expertise, and using specialist radon contractors approved by the Radon Council is recommended. Ongoing inspections and maintenance will also be needed, as will testing to confirm the system’s integrity after any works.
In all cases, ongoing testing is preferred to demonstrate that mitigation measures are working. Installations do not always work first time and might need modification or extension. Long-term validation is also prudent, either on an annual or 14-month basis to identify seasonal trends, as is retesting following any other building work, change of use, or installation of new heating and ventilation systems. In all events, professional testing and analysis is essential to radon safety.