It is used to detect hazardous concentrations of blood, nerve, and blister agents. The M256 replaced earlier generation kits, which were more difficult to use under battlefield conditions. In a combat situation, each person is responsible for observing his or her surroundings for signs of chemical warfare agent.
Warning signs vary depending on the chemical warfare agent used and the delivery method.
However, an unassisted individual can perform tests using the M256 when necessary. The M256 is used to test for the presence of hazardous concentrations of blood, nerve, and blister agents in vapor, and nerve and blister agents in liquid form. The vapor-sampler is similar to a miniature chemistry set. The difference is that M8 paper is specifically designed to react to nerve agents and blister agents in liquid form. The detection kit relies on a reaction between the chemicals and enzyme used in the vapor-sampler, or those impregnated within M8 paper, and a chemical warfare agent to produce a uniquely colored response.