It depends on where we're spraying the plastidip.
If you're in a well ventilated space, such as outdoors, a respirator shouldn't be required as the propellant gas will just dissipate like any other aerosol spray. But if you plan on spraying plastidip - or any other aerosol like it, such as spray paint - in a poorly ventilated space, a respirator should be used, because any gasses will build up in said space.