They are different from chemical warfare agents in that they are not man-made. Blister agents are also called vesicants or vesicant agents. A CWA is a chemical substance excluding riot control agents, herbicides, smoke, and flame, used in military operations to kill, seriously injure, or incapacitate through its physiological effects. Included are blood, nerve, blister, choking, and incapacitating agents. When a drop of chemical warfare agent is absorbed by the paper, it dissolves one of the pigments.
Mustard agent dissolves a red dye and nerve agent a yellow dye.
Detection paper can thus be used to distinguish between three different types of chemical warfare agents. A disadvantage with the papers is that many other substances can also dissolve the pigments. Consequently, detection papers should not be located in places where drops of solvent, fat, oil, or fuel can fall on them. Drops of water cause no reaction. The detection, identification, on-site evaluation, rendering safe, recovery, and final disposal of unexploded explosive ordnance.