How does it work? This Downtown Pet Supply no bark control collar senses your dog's bark. When your dog barks, a burst of Citronella (lemon) spray is emitted. The no bark control collar discriminates each bark from other external noises. A burst of citronella spray is emitted to deter barking only if both the vibration from vocal chords and the sound from the bark match the same criteria. The citronella spray is non-offensive to people and generally effective enough to distract your dog from whatever he is barking at. This is not a shock collar, shock collars use a painful shock to attempt to stop the barking. Using a shock collar is less effective and the pain induced to the dog usually increases anxiety, aggression and often worsens some behavior habits. We do not recommend shock collars. The Downtown Pet Supply citronella no bark collar is twice as effective as the shock collar and extremely safe, effective and humane! Brand New, Factory Sealed, Includes a 60 day Manufacturer Warranty *Note: Date on bottom of citronella canister is NOT an expiration date. It is a manufactured date. This product is not perishable.