Hazardous substances and radiation

What it is

Serious incidents involving hazardous chemicals or radiation are rare. Be Ready says that if you are involved in one it is important to know how to protect yourself and others. Hazardous substances can be solids, liquids or gases.

What it does to a home

The home becomes your shelter. For a chemical emergency nearby the instruction is go in, stay in, tune in, and the emergency services will say which areas should shelter and for how long. The distance and direction affected can change over time.

For a radiation emergency the UK Health Security Agency's advice is the same three steps. Go in: get indoors as soon as you can, close doors and windows and stay as far from external walls as possible. Stay in: staying indoors reduces your exposure to anything outside; turn off fans and air conditioning, close vents, and expect to be told what to do next, possibly after one to two days indoors. Tune in: monitor the news and follow official advice on GOV.UK. What you need to do depends on where you are relative to the release, so follow the advice for your location. You might be asked to decontaminate, and UKHSA publishes guidance on removing radioactive material from skin and clothes safely.

Because tune in may mean the radio, the power cuts advice to keep a battery or wind-up radio with the frequencies written down applies here.

Who warns you

The emergency services at the scene, and official channels afterwards. Be Ready says changes to advice in a radiation emergency come through radio, television, the internet, social media or the police. The UK Emergency Alerts system exists for life-threatening emergencies and sends a siren-like alert to every compatible phone in the affected area, based on where the phone is. Emergency alerts are only sent by the emergency services and by government departments, agencies and public bodies that deal with emergencies.

How the government assesses it

The National Risk Register 2025 assesses an accidental large toxic chemical release from an onshore major hazard site regulated under the COMAH Regulations, where operators have a legal duty to prevent accidents and the Health and Safety Executive enforces. The reasonable worst case is a toxic gas release near an urban area with fatalities and casualties, some long-term health effects, and vulnerable groups disproportionately affected. The register also covers a civil nuclear accident, which it calls extremely unlikely, with protective actions that could include sheltering, evacuation or stable iodine, and a radiation release from an overseas nuclear site close to the UK, where effects would depend on weather and distance. Chemical, biological, radiological and nuclear attacks are assessed separately under terrorism, and the terrorism page signposts that advice.

Where to look

• UKHSA chemical emergencies guidance and radiation emergencies guidance on gov.uk, both linked from the Be Ready page.
• Emergency Alerts at gov.uk/alerts.
• Related pages: poor air quality and pollution, fires in the home, terrorism.