A chemical weapon agent (CWA) is a chemical substance whose toxic properties are used to kill, injure or incapacitate human beings. About 70 different chemicals have been used or stockpiled as chemical weapon agents during the 20th century. These agents may be in liquid, gas or solid form. Chemical warfare involves using the toxic properties of chemical substances as weapons. Chemical Warfare is different from nuclear warfare and biological warfare which all together make up NBC (i.e, Nuclear, Biological and Chemical Weapons) also called as Weapons of Mass Destruction. In past Chemical Weapons are used as poisoned spears and arrows but technology has moved and the advancements in chemical weapons came into existence. The threat and the perceived threat have become strategic tools in outlining both measures and counter-measures. The predictions were secured by sending requests on the analysis from the scene of operations to the Defense Nuclear Agency, A chemical weapon is a specialized munition that uses chemicals formulated to inflict death or harm on humans. Choking agents are chemical toxins that directly attack the body's respiratory system when inhaled and cause respiratory failure. Common forms of choking agents include phosgene, chlorine, and chloropicrin. Blood agents. Blood agents interfere with the body's ability to use and transfer oxygen through the blood stream.