Citronella Bark Collars are designed to administer a short burst of Citronella Spray to distract a dog from barking. They come in a few varieties designed for small dogs and Big dogs and our standard Citronella spray bark collar is a good unit for all-round Dog barking issues. Basically they all work in a similar fashion. A short burst of citronella spray just at the right time. They are activated when the dog barks, usually by the sound of the barking or from the vibration of the vocal cords.