Chemical, biological, and radioactive substances purposely, accidentally, or after a natural disaster cause a lot of harmful effects on people and the environment. To prevent this harmful effect or at least minimize it, precautions must be immediately taken. These kinds of incidences have different importance for hospitals as victims apply first to hospitals, and they can decontaminate staff therein. Thus, different decontamination areas should be built in hospitals. Herein we discuss the decontamination that should be applied to victims. We provide information about the effects of nuclear weapons and the first aid rules for treating victims exposed to them. A clinical sign of radiation exposure is more obvious than that for biological and chemical weapons and because it can be detected more easily, fighting the clinical effects of nuclear weapons is easier than fighting the clinical effects of biological and chemical weapons. Biological weapons spread very easily and very rapidly from person-to-person, and the mortality rate can be high. Further, it causes a chaotic effect on society. Considering this feature of biological weapons, we will emphasize a number of precautions. Carrying and hiding toxic chemical weapons is easy. We will explain what should be done in case of exposure.