Radon is a colourless, odourless, radioactive gas derived from the radioactive decay of uranium present at varying but usually very small quantities in minerals and rocks. It is found at varying concentrations within our homes, places of work, outside and within caves and mines. Any exposure to radon is potentially harmful to our health by increasing our risk of lung cancer. The greater the concentration of radon, and the more time exposed to it the greater the risk, which is further exaggerated for those that smoke.

The levels of radon in caves and mines can vary by considerable amounts in relation to airflow, season and the source material. Radon concentrations are measured in Becquerels (Bq), that being the disintegration of one atom in one second, per cubic meter (m-3) of air. A sample of the range of concentrations within caves and mines in various regions is given in the following table:

Radon Concentration Bq m-3
Region Min Max Mean
Portland 10 974 454
Mendip 99 3,621 1,129
Forest of Dean 654 10,070 6,167
North Pennines 14 27,136 1,116
Yorkshire Dales 50 3,470 985
Peak District 9 46,080 8,258
South Wales 60 16,290 3,858

Radon exposure is another risk cave and mine explorers may wish to consider before undertaking a trip. Those at work underground, including those leading groups are required to comply with regulations relating to radon under the Health and Safety at Work act.

The third edition of Radon Underground has been updated to reflect the changes in regulations introduced in January 2018 and expanded to provide advice to those at work. These include changes in the threshold the regulations apply, together with the need to gather further measurements of radon to establish annual average.

A substantial program of radon measurements has been undertaken funded by the Association of Heads of Outdoor Education Centres, BCA and the Ministry of Defence plus some others. The results of that work have been incorporated into the third edition.

Radon Underground can be downloaded by clicking here

The data underpinning the summarised tables within the document can also be downloaded by clicking here