Three factors govern the level of radon gas in houses, the underlying geology and the design, construction and usage of the house and the time of day or year.
Since radon is produced from uranium, the amount of uranium in the ground and the ability of radon to diffuse to the surface is of prime importance. Even so, the geological factors affecting the level of ground surface radon are complex as the radon maps of the UK show.
Houses which are tightly sealed with double-glazing are more likely to trap higher levels of radon gas than houses with ill-fitting windows. The use of central heating also increases radon levels because the negative pressure that the central heating creates serves to draw in radon from under the floor. Houses made of stone may emanate radon gas from the walls if uranium is present in the stone. Ground floor premises are more likely to have elevated radon levels compared with those on the first or higher floors. Properties which are partially or wholly underground are particularly likely to harbour elevated radon levels.
Indoor radon gas levels also vary with time of day and time of year. Houses tend to be more sealed in winter with windows closed and heating switched on, whereas windows are often open in summer with no indoor heating. Consequently, indoor radon levels are at their highest in the winter months and at their lowest in the summer months. From knowledge of how radon levels vary with season, our long-term Radosure detectors can provide an accurate indication of the annual average radon level from a 3-month placement in the home.
Many of our customers, especially those interested in the radon gas level in a prospective property for purchase, require a much shorter-term radon measurement. Our 7-day Radosure detectors can provide an accurate snapshot of radon level and an indicator of whether radon levels are unduly high.
Radon is measured in units known as "Becquerels per cubic metre", written Bq per cubic metre. One Becquerel is one radioactive decay per second, so the units Bq per cubic metre refer to the number of radioactive decays from radon gas per second per cubic metre of air.
The average level of radon in UK homes is 20 Bq per cubic metre and the current Action Level above which remedial measures to reduce radon is recommended is 200 Bq per cubic metre. However, in view of the recent findings of increased lung cancer risk at exposures of 150 Bq per cubic metre, HPA’s Advisory Group on radon has made recommendations for new advice to be issued [click here – link to new advice section]. The recent findings suggest that exposure to radon gas accounts for 9% of lung cancers in Europe. In the UK, the HPA estimates that 1100 deaths from lung cancer may be attributed to radon exposure in the home. The HPA further estimates that 100,000 UK homes harbour radon concentrations above the current Action Level.
To read more about radon testing in the home, follow this link
To read more about radon testing in the workplace or in schools, follow this link.