I favor a combination of low tech and high tech. A simple thin glass container of chemicals per desired effect. Could even be done as a multi-part formulae that is harmless if one container is broken , however if two are broken they catalyze each other and the result accomplishes the desired effect. When a certain vibratory frequency is broadcast and reaches the desired levels, the containers break, the chemicals mix and are dispersed into the planes cabin. I recall a nasty little kitchen sink bit of chemistry where you fill a large glass christmas ornament with ammonia and place a cork into it. You then place this into a pint jar of bleach and cap it. When tossed into a room it clears out the people in a hurry. Cheap, simple and always reliable. Extrapolate this principle with nastier chemicals and a radio frequency to break the containers.