Chemical, biological, radiological, and nuclear defense (CBRN defense) or Nuclear, biological, and chemical protection (NBC protection) is a class of protective measures taken in situations where chemical, biological, radiological, or nuclear (including terrorism) hazards may be present. CBRN defense consists of CBRN passive protection, over-pressure suits, contamination avoidance, and weapons of mass destruction mitigation.
A CBRN incident differs from a hazardous material incident in both scope and intent. CBRN incidents are responded to under the assumption that they are intentional and malicious; evidence preservation and perpetrator apprehension are of greater concern than with Hazmat team incidents.