Described are methods for safer nitric oxide delivery, as well as apparatuses for performing these methods. The methods may include detecting the presence or absence of a nasal cannula, and stopping the delivery of nitric oxide or providing an alert if the cannula is disconnected. The methods may also include purging the nasal cannula if it is reconnected after a disconnection or if it is replaced by a new cannula. Other methods pertain to automatic purging of the delivery conduit if the elapsed time between successive deliveries of therapeutic gas exceeds a predetermined period of time.