The Multivet Spray Citronella Refill contain a gas mixture that is 100% safe for people animals and the environment. The propellant gas is the ozone friendly R134a. Used in many medical inhalation products it is harmless to pets and people. Most of us are familiar with citronella s pleasant lemony scent but it s also very effective as a training tool. Citronella is an essential oil that is derived from the stem and leaves of lemon grass and has been used in medicine for a thousand years.