Detection

The first thing a home owner, tenant, or employer needs to do, to see if their property has radon levels above the UK Government thresholds, is to measure it. First, it’s good to understand some basic principles of measuring radon, and then look at ways of measuring it in the home and the workplace. If you need help with detection and monitoring of radon, we can carry out a radon inspection and suggest the best methods for mitigation.

Basic principles of radon detection

What are 'normal' radon levels?

Most homes and workplaces across the UK have low radon levels.  Background levels are often quoted as 20 to 40Bqm-3, but some areas of the country could have higher background levels, and many properties will have levels up to 200Bqm-3. It is only when levels rise above the 200Bqm-3 (annual average) threshold for domestic properties, or 300Bqm-3 (annual average) for workplaces that an occupant needs to act.

How long to run radon tests

Radon gas concentrations can vary widely over time. Even during a day, week, month, or over a year. This is why the longer you can leave testing equipment, the better the results. Any measurement of less than 7 days has dubious relevance to understanding radon concentrations in a property/room. At 7 days a result has approximately 50% variance around the mean, which can provide simple ‘low’/’re-measure’/’action required’ set of ‘action’ bands for the occupier. At 1 month the result probably reflects the radon levels during that period of measurement. At 3 months a seasonal correction can be applied with reasonable accuracy, to reflect the annual average for a property.

Radon measuring methods

There are many different ways of measuring radon. Dtection methods range from complex scientific instruments, to simple passive detectors, or carbon canisters. For domestic and workplace measurements you do not need accuracy of less 10Bqm-3, as measurements finer than this are not required for understanding radon and its remediation in a property. For normal home and workplace measurement passive radon detectors and electronic radon monitors are most widely used.

⇒ Compare passive and electronic radon detectors

Measuring radon in the workplace

Under the Health and Safety at Work act 1974 an employer bears responsibility for the health and safety of employees, and in the Ionising Radiations Regulations 2017 (IRR17) the standards are set to meet these responsibilities. The ‘Annual Average’ Action level for the workplace is 300Bqm-3.

Measurement in the workplace is usually conducted using passive detectors for at least a month, and more often a 3 month period, as this better reflects workforce exposure. These results are usually corrected to reflect the annual average.  Measurements use one passive detector for each room, or open workspace up to 250m2. Placement should be in rooms/offices that are considered fully-occupied by employees, and consideration made of rooms partially or temporarily occupied by staff. This passive detector test can provide the baseline evidence for radon remediation, or otherwise, depending on results.

Electronic radon monitors can be used as a supplement to passive detectors, providing on-going or spatial detail to support the passive detector tests.

Measuring radon in the home

Domestic properties should aim to keep radon levels below 200Bqm-3 to comply with UK Government guidelines; known as the radon Action level. The standard means of determining if the radon in the home is below the domestic Action Level is to use two passive detectors over a 3 month period. Often residents first become aware of radon when selling or buying a property, when they might be asked to supply/ or be supplied with radon information on their property.

See Buying and selling a home

To conduct a standard domestic test, one detector is placed in the main Living Room, and one in the main bedroom. A minimum of 3 month placement is required to allow a seasonal correction to be applied, resulting in an Annual Average result for the whole property. Passive detectors need to be analysed in a laboratory to get the result. A paper document is supplied to the purchaser to state the radon levels in each room, and an Annual Average result.

If an occupant/owner requires information for themselves, and do not require paperwork to authenticate their radon results, then an electronic monitor can be used. These can produce results within a day, and will show the reader a short-term and various longer-term measurements on an on-going basis, depending on the model. These type of instruments can be used to determine averages across a house in a short period of time, but the results can be misunderstood if understanding of the basic monitoring principles (above) are not adhered to. The user must be sure that they keep good records of results and the monitoring period to reduce inaccuracy and provide good evidence.

It is recommended that your monitor results be discussed with a radon specialist before any remedial action is undertaken, as the results can lead to confusion and misinterpretation, without a wide knowledge of radon and its remediation.

If your radon measurements show your property is above the 200Bqm-3 action level, then radon remediation is required.