CBRN Threat Awareness and Agent Recognition
Recognition begins with pattern recognition at the scene, not with a laboratory result. The candidate should be able to sort a threat into chemical, biological, radiological, nuclear, or high-yield explosive and then narrow within the class.
Chemical
The main families are nerve (organophosphate anticholinesterases such as sarin, soman, VX), blister/vesicant (sulfur mustard, lewisite), blood (cyanide, arsine), and choking/pulmonary (chlorine, phosgene). Toxic industrial chemicals and toxic industrial materials are statistically more likely than a weaponized agent and produce the same syndromes. Recognition clue: nerve agent produces miosis, salivation, lacrimation, urination, diarrhea, bronchoconstriction, bradycardia, and fasciculations, with rapid onset after a point-source release. Vesicants produce delayed (hours) skin erythema and blisters, eye pain, and airway injury; onset delay is the classic trap. Cyanide causes rapid collapse, seizures, and cardiovascular failure with few early signs.
Biological, Radiological, Nuclear
Biological agents show an incubation interval, an epidemic curve, and clustered febrile or respiratory presentations; nothing is visible at the scene. Radiological material produces no immediate symptoms, so casualties are detected by instruments or by a history of exposure, not by appearance.
Traps
Bitter-almond odor for cyanide and cherry-red skin are unreliable and often absent. Not every incident has a smell, a mist, or a visible device. Do not exclude a chemical cause because casualties walked to the aid station, and do not assume a single casualty means no release.
Rule of thumb
Syndrome + speed of onset + scene geometry. A shared, rapidly evolving toxidrome among people in one place at one time favors a chemical agent; a delayed, spreading illness pattern favors biological.