|1. The product is kept separate by putting it in a nylon bag inside the can. |
2. The propellant surrounds the bag, producing an inwards pressure to push the product out.
3. The actuator. When you press down on the actuator, it opens ...
4. ... the valve and allows the product to be pushed out. The structure of the valve and the nozzle help determine the features of the spray.
5. The nylon bag is usually crimped into the join between the can and the valve cup. Often, it is softened with steam so that it is more flexible and crimps more easily.
The aerosols are fully assembled (except for the actuator) before they are filled.