Radon is a naturally occurring radioactive gas, produced as uranium decays to lead. Where Radon rises outside buildings it disperses harmlessly, however, harmful radon concentrations can occur where the gas rises within buildings.
Prolonged exposure to radon can cause health problems. Approximately 2,500 deaths per year are attributed to lung cancer resulting from radon inhalation. Exposure to radon is the biggest single cause of radiation exposure to the population of the UK.
Radon concentrations occur in buildings because temperature differentials and air movement will tend to produce lower internal air pressure which will draw the gas into the building through small gaps and cracks in the fabric (see Figure 1).
Radon concentration is measured in Becquerels (Bq m3). In most homes the average level of radon is 20 Bq m3, However, where levels exceed 200 Bq m3 - the National Radiological Protection Board action level - building owners should take measures to reduce radon concentrations to the lowest practicable levels.