As the air pressure inside the building is the main factor affecting the entry of radon gas, techniques which alter this pressure differential are the most successful ways of remediating buildings with high radon levels. Two such techniques are the use of specialist positive pressure units and retro-fitting a radon sump beneath the building. It must be recognised that radon mitigation is a specialist and sophisticated service, where an understanding of the science of radon movement is required. Some techniques, such as the use of extract fans to increase ventilation can in fact exacerbate the problem and cause greater volumes of the gas to be drawn into the property. It would therefore be unwise to place such responsibility in the hands of an unskilled contractor. Reducing radon levels in properties with basements is particularly difficult, due to the large area of low pressure created by the basement. A system should be used that will not only reduce radon levels in the basement but prevent the gas from being displaced into the ground-floor accommodation. Waterproofing to the British Standard BS 8102 must also be achieved if the basement is to be useable. Given the nature of radon entry into buildings, radon should be viewed as something that needs to be managed, not simply to be ‘fixed’. Even with many years’ experience in dealing with radon mitigation, a specialist contractor may not always solve the problem at the first attempt. No two buildings are identical, as is the geology beneath any two plots of land. It is therefore imperative that a radon test is done after remediation works have been carried out, to determine whether they have been effective. Where very high levels of radon have been found in a building, it may take several attempts and various combinations of techniques to sufficiently lower the concentration of the gas.