The growing threat of biological and chemical attacks propelled all Special Forces Units to receive training to function under extreme conditions and to handle hazardous materials. Six created the Chemical, Biological, Radiological, Nuclear (CBRN) Threat Unit, formalizing a standard in best practices in the event of such attacks. CBRN operators are experts at handling Level 4 crisis hotzones.
- The term "CBRN" by itself only refers to its respective hazards and doesn't specify the organization or unit. There are real-life units which are designed to respond to CBRN threats with "CBRN" in their names, but the game's version is fictional. "CBRN defense" refers to protective measures taken in such situations.