Pneumatic, because a universal system is needed to disperse the spray while many liquids are not easily compressed and require quite a lot of pressure to do so which would make the can heavy and costly, and negatively affect control of the release rate without a much higher precision nozzle area. Therefore a gas is pressurized as the propellant.
In cases where the gas itself is the product, that gas may liquify under pressure and not require a separate propellant but it is still the evaporation into a gas that propels it.
Its depend on the application where u want to use it because both are made for different application. But in generally people refer pneumatic because of low cost & maintenance.
Both - Called an air over hydraulic system. The pressurized gases are uses to pressurize the oil/product.
I would say that it is more pneumatic because its volume is constant.
please state why
