Chemical, Biological, Radiological and Nuclear (CBRN) and HazMat Incidents

In this section, we provide an overview of chemical, biological, radiological and nuclear (CBRN) and hazardous materials (HazMat) incidents, along with the specialist response required. This is not a full training package, but a structured guide to the key concepts, terminology and approach that commanders and responders must understand.

HazMat vs CBRN – What Is the Difference?

Although the terms HazMat and CBRN are often used separately, they describe similar types of incidents. The key difference is the cause, not the effect:

• HazMat (Hazardous Materials) incident: an accidental release that results in illness, injury or contamination.
• CBRN incident: a deliberate release of chemical, biological, radiological or nuclear material, usually by perpetrators or terrorists.

For example, a chlorine release may be accidental (HazMat) or intentional (CBRN). The cause changes the classification, but our operational response principles remain broadly the same.

Roles, Responsibilities and Decontamination

In HazMat and CBRN incidents, the usual focus on triage, treatment and transport is expanded to include decontamination. Casualties often need to be decontaminated before they can be treated or transported safely.

Working with Fire and Rescue

• Fire and Rescue play a leading role in mass decontamination.
• Ambulance services generally decontaminate those who are contaminated and injured.
• Fire and Rescue typically decontaminate those who are contaminated but not injured.

Police Responsibilities

• Secure and manage the inner cordon.
• Support early decontamination and evidence collection, especially in CBRN incidents.
• Search for secondary devices or additional threats.
• Protect other emergency services and lead or support investigations.

Zones and Cordons: Hot, Warm and Cold

In HazMat and CBRN incidents, the operational area is divided into three main zones:

• Hot Zone: the contaminated area and site of the incident.
• Warm Zone: the area where decontamination is carried out – often a corridor between hot and cold zones.
• Cold Zone: the “clean” area where decontaminated casualties and assets are managed, treated and transported.

The cold zone will usually have its own outer cordon to control access and egress.

The warm zone is almost always positioned upwind of the incident to prevent contamination spreading through vapour or droplets.

Use of Hot, Warm and Cold Zones in Firearms / MTA Incidents

The same terminology is also used in marauding terrorist attacks (MTA) and firearms incidents, but with different definitions:

• Hot Zone: where perpetrators are active (e.g., ongoing shooting or violence).
• Warm Zone: areas the perpetrators have moved through, where specialist medical teams may enter to start treatment and evacuation.
• Cold Zone: secure areas where business as usual can continue and conventional treatment can be delivered.

Steps 1–2–3 Plus – Recognising Suspicious Clusters

The Steps 1–2–3 Plus approach helps responders recognise abnormal patterns:

• 1 casualty: unconscious with no obvious cause – approach with standard safety precautions.
• 2 casualties: especially in a confined space (including inside a building) – be more suspicious and consider specialist support.
• 3 or more casualties: consider this a potential major and hazardous incident that requires a specialist response.

In such cases, self-decontamination may be required early, especially where the nature of the release is unknown or accidental.

Indicators of a Possible Chemical Release

When approaching a scene, look for “battlefield indicators” that something out of the ordinary may be occurring:

• Unexplained dead animals in a localised area.
• Lack of insects where you would normally expect to see them.
• Unusual liquids, residues or oily substances on the ground.
• Abnormal vegetation – withered, scorched or dead patches surrounded by healthy growth.
• Unexplained odours (chemical, unusual or pungent smells).
• Low-lying vapour, mist or fog inconsistent with weather conditions.

These indicators do not confirm a chemical incident but should prompt heightened caution and consideration of a HazMat / CBRN response.

Decision-Making and Specialist Advice

As an incident commander, you are responsible for deciding whether decontamination is required. This decision should be based on:

• Information from subject matter experts.
• Advice from tactical advisers (TACADs).
• Guidance from National Incident Liaison Officers (NILOs) or similar roles.

Remember, advisers support your decision-making – they do not replace it. You remain accountable for operational decisions.

Types of Decontamination

1. Initial Operating Response (IOR) – Improvised / Dry Decontamination

Initial Operating Response (IOR) is the current UK model for rapid, improvised decontamination and is designed to be used by frontline responders without waiting for specialist teams. It is based on:

• Dry decontamination using absorbent material (e.g. NHS “blue roll”).
• Prompt action – ideally within 15 minutes of exposure.
• Self-decontamination under clear instruction.

Evidence from Defence CBRN Centre and Public Health England showed that traditional warm water “rinse–wipe–rinse” methods used in civilian settings were not only ineffective, but could actually worsen contamination by opening the pores and driving chemicals through the skin. Dry decontamination using absorbent roll was shown to be up to 3,000% more effective.

Initial Operating Response – Practical Process

Frontline responders from ambulance, fire and police are now all trained in IOR. The typical sequence is:

1. Move casualties uphill and upwind from the source of contamination to a safer area.
2. Provide plastic bags and instruct them to remove outer clothing, placing garments into the bags.
3. Tie the bags securely and turn them upside down to prevent leakage in windy conditions.
4. Move casualties forwards (e.g. 10 paces) to a second line where absorbent roll is available.
5. Instruct them to use a “blot–pat–rub” method with the blue roll, concentrating on exposed areas from head downwards.
6. Ensure they remove items such as glasses which may hold contamination.
7. Place used roll into plastic bags, secure these, and then move casualties forward again.
8. At distance, question them about symptoms (e.g. burning, itching, breathing difficulty) and decide whether further cold water decontamination or priority treatment is required.

To keep control, limit each group to around 25 casualties. For each group, aim for:

• One commander: gives clear instructions to the group.
• One compliance officer: watches for and corrects non-compliance.
• One demonstrator: shows the actions, especially helpful where English is not the first language.

Communication should be firm, honest and calm. Do not make promises you cannot keep; keep people informed about delays and next steps.

2. Interim Decontamination

Interim decontamination is usually set up quickly by Fire and Rescue. It often involves:

• Using a fire hose slung over a ladder between appliances to create a shower.
• Basic modesty screening where possible.
• Rapid throughput of large numbers in a short time.

Fire services can generally establish this within 5–6 minutes of arrival, given typical UK response times.

3. Clinical Decontamination

Clinical decontamination is carried out by specially trained clinical staff who can:

• Decontaminate casualties safely.
• Manage injuries and medical problems at the same time.

In the UK, this is usually undertaken by Special Operations Response Teams (SORT), who are frontline ambulance staff with additional specialist training. In some areas, they are also trained to work in firearms / MTA warm zones.

4. Mass Decontamination

Mass decontamination is the rapid processing of large numbers of contaminated but otherwise uninjured people. This is primarily the responsibility of the Fire and Rescue Service, using purpose-designed mass decontamination units and systems.

Specialist Personnel and Command Support

HazMat and CBRN incidents require additional specialist roles, including:

• Tactical advisers (TacAds) – provide expert incident-specific advice.
• National / local incident liaison officers (NILOs) – link with other agencies and specialist assets.
• Decontamination officers – manage the decontamination process and SORT teams.
• Specialist-trained warm-zone responders – those permitted to operate in hazardous environments with appropriate PPE and training.

These roles support your risk management process: balancing the need to protect your staff against the need to maximise casualty survival through timely decontamination and evacuation.

Key Takeaways

• HazMat and CBRN share similar response principles; the main difference is whether the release is accidental or deliberate.
• Zones are divided into hot (contaminated), warm (decontamination) and cold (clean).
• Initial Operating Response with dry decontamination is now the default first step for chemical exposure in the UK.
• Decontamination responsibilities are shared across ambulance, fire and police, with specialist teams providing advanced support.
• As a commander, you retain decision-making responsibility but should actively use specialist advisers.

With the right structure, clear communication and evidence-based decontamination methods, responders can significantly reduce harm and improve outcomes in HazMat and CBRN incidents.