HMP Dartmoor: HSE issues censure over redon exposure
Concerns were first raised back in February 2023
Last updated 13th May 2026
His Majesty's Prison and Probation Service (HMPPS) is facing significant repercussions after an investigation by the Health and Safety Executive (HSE) found that radon levels at HMP Dartmoor exceeded safe limits.
Radon is naturally occurring radioactive gas, and is known to contribute to approximately 1,100 lung cancer-related deaths in the UK annually, according to the UKHSA.
There's more details about radon on the UKHSA website.
At HMP Dartmoor, concerns about radon exposure were first raised in February 2023.
Monitoring revealed radiation levels significantly higher than the average 20 bq/m3 found in UK homes, with recordings from March 2020 showing the prison’s kitchen had soared to 2,988 bq/m3.
HSE inspectors found the radon exposure at HMP Dartmoor had been prolonged over several years, prompting enforcement actions in February and December 2023.
More here: Government locked into £4m-a-year spending on HMP Dartmoor
Despite these measures, the prison service failed to adequately manage the radiation levels, which has now led HMPPS to decide on mothballing the crumbling Victorian-era facility in 2024.
More here: Dartmoor Prison closes 180 cells after radioactive gas detected
The HSE legal services team has now authorised a Crown Censure, which is the strongest action available against a Crown body.
This authorisation signifies significant breaches of health and safety law, though it does not equate to a criminal conviction and carries no financial penalties.
Instead, if confirmed in an upcoming formal hearing, the censure will serve as a public and lasting reprimand for serious safety failures.
Upon confirmation, it will highlight HMPPS's failure to comply with safety regulations and create a permanent public record of these infractions.
Full UKHSA statement
The Health and Safety Executive said: "The Health and Safety Executive (HSE) has today notified His Majesty's Prison and Probation Service (HMPPS) of its intention to issue a Crown Censure following an investigation into radon exposure at HMP Dartmoor in Devon.
"The investigation found that HMPPS failed to adequately manage radon exposure at the prison.
"The Health and Safety Executive was first notified by HMPPS of suspected overexposure in February 2023.
"Subsequent monitoring confirmed that radon concentrations in areas of the prison, including prisoner accommodation, resulted in prisoners and staff being exposed to radiation levels above the legal limit.
"HSE’s investigation concluded both prisoners and staff had been exposed to radon significantly above the specified dose limits for a prolonged period of time.
"HSE took enforcement action highlighting breaches of the regulations in both February and in December 2023. HMPPS decided to mothball HMP Dartmoor in 2024.
"Following an investigation by HSE inspectors, a file was passed to HSE’s legal services division for review, which in accordance with Code for Crown Prosecutors has authorised a Crown Censure.
"A Crown Censure is the maximum sanction available to HSE against a Crown body. A decision to authorise a Crown Censure is not a formal finding of guilt - is equivalent to a decision to authorise criminal charges, in line with the Code for Crown Prosecutors.
"Following the decision to issue a Crown Censure, a formal hearing will take place to confirm the censure. If a censure is confirmed at a hearing, it acts as an official reprimand and provides a lasting, public record of a Crown body's failure to comply with the law. There is no financial penalty."
'The wellbeing and safety of staff and prisoners is our priority'
A HMPPS spokesperson said: “The wellbeing and safety of staff and prisoners is our priority.
"Since 2022 we have strengthened radon monitoring and mitigation across the estate.
“We have noted the Health and Safety Executive’s decision to begin Crown Censure proceedings, and it would be inappropriate to comment further while these are ongoing.”