Prison service faces sanctions over exposure of inmates and staff to deadly radioactive gas

The prison service faces severe sanction by the health and safety regulator after it exposed staff and inmates to dangerous levels of deadly radon gas. 

An investigation found failures by HM Prison and Probation Service (HMPPS) meant inmates and staff at HMP Dartmoor, in Devon, were breathing in radiation levels above the legal limit for a "prolonged period of time".

Radon is a naturally occurring radioactive gas, formed by the decay of uranium in rock and soil.

The HSE say breathing it in is the second largest cause of lung cancer in the UK, leading to more than a thousand deaths a year, according to the UK Health Security Agency.

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The watchdog took enforcement action twice in 2023, warning that regulations were being breached. The prison was mothballed in 2024.

Monitoring since concerns were raised in 2023 confirmed radon concentrations were found in areas of the prison, including the accommodation.

Following their investigation the HSE has authorised a Crown Censure, which is the maximum sanction the regulator can impose on a government body, and is the equivalent to authorising criminal charges.

Sky News understands hundreds of former staff and inmates have sought legal instruction, believing they have been affected by the issue at Dartmoor Prison.

Radon is everywhere, but there are higher levels in areas with richer concentrations of granite, such as the South West of England, Devon and Cornwall.

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".

(c) Sky News 2026: Prison service faces sanctions over exposure of inmates and staff to deadly radioactive gas