The physiological processes through which this is made possible is quite simple. The flash of light momentarily activates all sensory pigment in the retina, making vision impossible for approximately five seconds until the eye restores the pigment to its original, unstimulated state. Subjects affected by flashbangs describe seeing a single frame for the five seconds (as if their vision was "paused") until it fades and normal sight returns. This is because the sensory pigments which have been activated continue sending the same information to the brain until they are restored to their resting state, and the brain translates this continuous information into the same image. The incredibly loud blast emitted from the grenade contributes to its incapacitative properties by disturbing the fluid in the semicircular canals of the ear. The semicircular canals consist of three half circles of tubing, each oriented in one of the three planes of motion, that are filled with saline. The walls of the tubes are lined with hair cells which use their small, hairlike cilia to detect the motion of the water. This establishes a person's sense of balance and movement through space. When a flashbang detonates, the water in the semicircular canals is disturbed, and with it the subject's sense of balance. The phenomenon is similar to spinning rapidly in one direction, and suddenly stopping. The sensation that the room is moving comes from the movement of the water in the inner ear.

Upon detonation, the fuse/grenade body assembly remains intact and produces no fragmentation. The body is a steel hexagonal tube with holes along the sides which allow a blast of light and sound to be emitted. This is done to prevent injury from shrapnel. However, injuries resulting from the concussive properties of the detonation sometimes occur. The filler consists of about 4.5 grams of a pyrotechnic metal-oxidant mix of magnesium and ammonium perchlorate.