Prevention and prophylaxis are commonly used in medicine to prevent illness. However, these do not apply in this instance. Prevention is what intelligence and law enforcement agencies do. Medical personnel have neither the training nor resources to prevent a terrorist attack. Prophylaxis, in the form of immunization, is a common way to prevent disease, but there is no known prophylaxis for chemical agents, and even if there were it would be impractical to immunize a population at risk because we do not know what population is at risk.
Medical personnel have the task of taking care of casualties after the event has occurred.
This includes diagnosis, management, and triage of casualties while preventing spread of the disease or agent. Preparation for this includes knowledge and equipment. The responder must have knowledge of the agent, its effects, and countermeasures and knowledge of how to protect self and others, which includes decontamination of self and others. Equipment includes material for countermeasures, such as antidotes if known, and material for protection, such as protective clothing and masks. In rural areas medical facilities there may be supplies of atropine and 2-PAMCl for use in insecticide poisoning, but in cities these supplies are small at best.