Modern anaesthetic agents are very potent, so it is easy to inadvertently overdose an animal. To avoid this, and also to ensure that onset (induction) of anaesthesia is smooth and that an appropriate depth of anaesthesia is produced, an anaesthetic vaporiser should be used.
These devices are designed to deliver a precise concentration of anaesthetic, even when the temperature and rate of gas flow are changed. A carrier gas flows through the vaporiser, and this then delivers a set concentration of anaesthetic to the animal. As all anaesthetics depress respiration, it is best to use oxygen as the carrier gas. Anaesthetic vaporisers are usually mounted on an anaesthetic machine.