ASBESTOS & HAZARDOUS SUBSTANCES
RADON OF THE LOST ARK
Peter Warman, Innovation Manager at Ground- Gas Solutions Ltd, opens our eyes to the potential danger of the radon gas that is lurking in buildings, both old and new.
WHAT IS RADON? Radon is a gas produced from the decay of uranium, a naturally occurring element in the earth’s crust. Radon is radioactive with a half-life of about four days.
THE RADON HAZARD Radon is present in outdoor and indoor air, usually in small amounts. We are breathing it in and out all the time. If a radon atom decays while inside our lungs, the alpha radiation released may damage lung cells. This has the potential to cause lung cancer. It is estimated that 1,100 people die prematurely every year from radon exposure, just in England and Wales.
Uranium, and therefore radon, is known to be associated with rocks and soils which include granite and shale. The probability of encountering high radon levels has been mapped for the UK in the ‘Indicative Radon Atlas’. Areas where 1% or more buildings (present and future) are likely to fall above the domestic Action Level are classed as Radon Affected Areas. It’s important to remember that the atlas is indicative; the only way to know if radon levels really are high is to test for it.
TESTING FOR RADON Radon concentrations in the UK are measured in Becquerels per cubic metre (Bq m-3) or 1 radon atom disintegration per second per cubic metre. It is commonly tested for with passive ‘track etch’ detectors. To observe the likely worst case radon levels, testing in the winter months is recommended. Tests should be done in areas of highest occupancy to get an indication of exposure. Radon concentrations are highly variable, therefore a time averaged concentration is usually taken over
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a test period of 90 days. Within larger buildings, a good spread of detectors is usually needed as radon concentrations often vary from room to room. Interpretation of radon testing results is key.
LEGAL REQUIREMENTS High radon levels within buildings can be considered an engineering fault. Therefore employers have a legal duty, under the Ionising Radiation Regulations 1999, to ensure that employees are not exposed to concentrations exceeding the workplace Action Level of 400 Bq m-3. Should radon levels exceed this, provisions should immediately be put in place to reduce radon levels or manage exposure. Where provision for radon mitigation is not immediately put into place, employment of a Radiation Protection Advisor may be needed to manage radon dosage; this is done by restricting occupancy to the building or to certain rooms.
RADON MITIGATION Solutions exist to reduce radon in existing buildings. A common and often effective solution is the installation of active radon sumps. This involves the removal of a small volume of fill from beneath a building, with pipework sealed into this void to the outside air, with an in-line electric fan. The fan creates an area of negative pressure beneath the footprint which radon will preferentially migrate to. It will then be safely exhausted, typically above the building eaves and away from windows or doors.
NEW BUILDINGS New buildings in Radon Affected Areas must be equipped with either basic or full radon protection
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Multiple radon sumps on a large building footprint.
“IT IS ESTIMATED THAT 1,100 PEOPLE DIE PREMATURELY EVERY YEAR FROM RADON EXPOSURE, JUST IN ENGLAND AND WALES.”
measures. This involves either a radon proof membrane, radon sump, or a combination of both. However, in practice, achieving a gas tight barrier beneath a building should not be considered basic.
VALIDATION Radon mitigation measures, both in new builds and existing buildings, do not always work first time. Buildings should be tested for radon after measures are installed to demonstrate that they work. This usually involves the use of passive track etch detectors. Should levels still be unacceptably high, mitigation systems may be modified to improve their effectiveness.
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