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What is radon?

Radon is a colourless, odourless radioactive gas formed by the radioactive decay of the small amounts of uranium that occur naturally in all rocks and soils.

Where is radon found?

Radon is everywhere; formed from the uranium in all rocks and soils. Radon levels are low everywhere outdoors and for many areas indoors and the risk to health is small.

The level of radon in a building cannot be predicted reliably, but a detailed radon potential map was published in 2007 showing Radon Affected Areas or ‘hotspots’ in England and Wales.

Radon ‘hotspots’ are areas where more than 1% of domestic properties have levels greater than 200 Becquerels per cubic metre of air (Bqm-3).

Why is radon a risk to health?

The radioactive elements formed by the decay of radon can be inhaled and enter our lungs.

Inside the lungs, these elements continue to decay and emit radiation, most importantly alpha particles. These are absorbed by the nearby lung tissues and cause localised damage. This damage can lead to lung cancer.

Radon causes over 1,100 deaths from lung cancer each year in the UK.

Half of these deaths occur among the quarter of the population who are current smokers.

The higher the radon levels and the longer the exposure to it, the greater the risk - especially if you smoke.

What level of radon is a cause for concern?

Radon is measured in Becquerels per cubic metre of air (Bqm-3). The average level in UK homes is 20 Bqm-3.

For levels below 100 Bqm-3, your individual risk remains relatively low and not a cause for concern. However, the risk increases as the radon level increases.

Within domestic properties Public Health Wales recommends that radon levels should be reduced where the average is more than an Action Level of 200 Bqm-3.

This Action Level refers to the annual average concentration as measured using two detectors (in a bedroom and living room) over three months, to average out short-term fluctuations.

A Target Level of 100 Bqm-3 is the ideal outcome for remediation works in existing buildings and protective measures in new buildings.

If the result of a radon assessment is between the Target and Action Levels, action to reduce the level should be seriously considered, especially if there is a smoker or ex-smoker in the home.

For workplaces where people usually spend less time than at home (i.e. reduced exposure) then levels are different.

Health and safety legislation requires employers in radon ‘hotspots’ assess radon exposure. This duty also applies to any workplace where there are underground workplaces, even if they are not in a radon hotspot.

The Ionising Radiations Regulations 1999 come into effect where radon is present above 400 Bqm-3 and employers must take action to reduce radon exposure in these cases.

Where are the radon ‘hotspots’ (Radon Affected Area)?

The level of radon in a home or building cannot be predicted reliably, so if you are in or near a radon hotspot we advise that you measure the levels.

An indicative map of radon affected areas in England and Wales, produced by Public Health England and British Geological Survey, is available here.

Find out how to measure radon in your property here.

Measuring radon in the home and other buildings

Radon detectors are safe and simple to use e.g. they can sit on a shelf. They are small hollow plastic shells containing a piece of clear plastic that records the damage caused by radon.

The detectors do not emit anything and do not collect anything dangerous. However, they can be damaged by heat or submersion in water and should not be opened.

The amount of radon varies over time and from room to room in a home. The test is carried out over three months to allow for variations in levels.

The test is to determine your exposure, this is why we recommend testing the living area and bedroom as these are the rooms you and your family use the most.

Actions to remedy / reduce exposure

Some simple actions such as sealing around loft-hatches, sealing large openings in floors and extra ventilation do not reduce radon levels on their own.

When combined with other effective measures, they can improve the reduction of radon levels. Completely sealing floors is difficult and can cause rot in wooden floors.

Examples of effective measures include:

  • Radon sump - an active radon sump, fitted with a fan, is the most effective way to reduce indoor radon levels. Sumps work best under solid floors and under suspended floors if the ground is covered with concrete or a membrane. Occasionally, passive sumps without a fan may reduce radon levels.
  • Positive ventilation - a small quiet fan blows fresh air, usually from the roof space, into the building.
  • Natural under-floor ventilation - many homes and some workplaces have a suspended ground floor with a space underneath. Good ventilation of this space can reduce radon concentrations.
  • Active under-floor ventilation - a fan is used to either continuously blow air into or extract air out from the space below a suspended floor. This can be used when natural under-floor ventilation is inadequate to reduce radon level.

Further information

For more information about radon please visit the UK Radon Reference website.