3.2 Site preparation – protection from radon gas
Radon is a naturally occurring, radioactive, colourless and odourless gas that is formed where uranium and radium are present. It can move through cracks and fissures in the subsoil, and so into buildings. The amount, or activity, of radon is measured in becquerels (Bq). Where this gas occurs under buildings, the external walls contain it and the containment of radon can build up inside the buildings over the long term posing a risk to health.
Exposure to high levels of radon for long periods increases the risk of developing lung cancer. To reduce the risk, all new buildings, extensions and conversions, built in areas where there might be radon concentration, may need to incorporate precautions against radon.
Ionising Radiations Regulations 1999 - Occupational exposure to natural radiation sources, including radon gas, is the subject of regulatory control. This is in line with the most recent revision to the Euratomic Basic Safety Standards Directive (Council Directive 96/29/EURATOM) that establishes a common basis for radiation protection legislation in all European Member States. Regulation 3 of the Ionising Radiations Regulations 1999 (SI 1999/3232) sets a national reference level for radon gas in workplaces of 400 Bq/m3 averaged over any 24 hour period. An employer or self-employed person responsible for a workplace is required to measure radon levels in the workplace on being directed to do so.
If radon levels are found to be in excess of the reference level, the regulations require that measures be taken to safeguard the health of workers.
Further information on the Ionising Radiations Regulations 1999 and the Health and Safety at Work, etc. Act 1974 as they relate to radon in workplaces can be found on the Health and Safety Executive (HSE) website at http://www.hse.gov.uk/radiation/ionising/radon.htm.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirements of this standard in so far as is reasonably practicable, and in no case be worse than before the conversion (regulation 12, schedule 6).
“Radon probability areas” have been designated by testing dwellings. Where tests on existing dwellings show that at least 1% of the dwellings in that area are likely to have a radon concentration above 200 Bq/m3 (the action level) the area is designated as a “radon probability area”.
Radon maps - The Health Protection Agency (now Public Health England (PHE)) and the British Geological Society jointly worked on detailing mapping in Scotland of radon potential. The report providing an overview of this work, titled "Indicative Atlas of Radon in Scotland", was published in July 2011 and is available to view or download from the PHE’s “UKradon” website at http://www.ukradon.org/. The resulting high definition digital map indicates areas in Scotland with elevated radon potential. Although prepared by testing dwellings at the more onerous action level of 200 Bq/m3, the map provides an indicative picture of areas of the country where radon levels are likely to be higher and may be consulted in respect of non-domestic buildings.
A site, and ground immediately adjoining a site, should have radon gas made safe so that it is not allowed to be contained in a building at levels that are considered harmful to health. The term ‘ground immediately adjoining’ is intended to cover ground that is disturbed as a direct result of the works.
Workplaces are less of a risk than dwellings because, generally speaking, people spend less time at work than at home and workplaces usually have better ventilation provision.
Large buildings tend to be mechanically ventilated and this may result in the dilution of radon gas. The action level of 400 Bq/m3 in work places makes it easier to stay within that level than the lower level of 200 Bq/m3 for dwellings.
Guidance on reducing radon in workplaces can be found in the BRE publication FB 41 “Radon in the Workplace – A Guide for Building Owners and Managers”. Additional radon protective measures can be found in BRE publication BR 211 – “Radon: guidance on protective measures for new buildings”. Although produced mainly for new dwellings the guidance can also be useful for providing protection advice for any small building.
Additional guidance on the installation of radon protection measures in large buildings is available in BRE Good Building Guide GG 75 “Radon protection for new large buildings”. This publication should be read in conjunction with BR 211.