One of the clever ideas with the air squib is that it has a built-in remote control. This allows the actor to focus on acting, falling and reacting to “being shot”, not needing to fiddle with hidden switches and hiding wires up the sleeve. Here is a clip from a scene with actor Jon F. Merz who not only acts, but has also been training in martial arts for a long time, and that shows in his impressive fall. The freedom of movement using the air squib is also often commented upon, and liked by both actors and stuntmen. In other words, very little rigging and “stuff” is needed on the actor.
An extra advantage of not setting off the effect himself is that the actor is often a little “surprised” when the hit goes off, helping the actor in the reaction, and adding a little extra shock value to the scene.
English 
Spanish