A nasal delivery device for delivering substance to a nasal cavity of a subject, the delivery device comprising: a substance supply unit for supplying a dose of substance to be delivered to the nasal cavity of the subject, the substance supply unit including an inlet and an outlet; a nosepiece unit including a nosepiece for fitting to a nasal cavity of the subject and being in fluid communication with the outlet of the substance supply unit; and a mouthpiece unit including a mouthpiece in fluid communication with the inlet of the substance supply unit through which the subject in use exhales such as to entrain substance from the substance supply unit and deliver the same through the nosepiece; at least one temperature modifier for reducing a temperature of the exhaled air flow such as to reduce the absolute humidity thereof; characterized by: the substance supply unit comprising a container chamber for receiving a substance-containing container which contains a dose of substance; the container chamber and the nosepiece comprising a unitary, replaceable component; the at least one temperature modifier comprising a plurality of elongate channels; the plurality of elongate channels allowing a flow therethrough at a flow rate of at least about 10 l/min at a pressure of less than about 2 kPa; and the plurality of elongate channels providing a pressure drop of not more than about 0.5 kPa to the exhaled air flow. a substance supply unit for supplying a dose of substance to be delivered to the nasal cavity of the subject, the substance supply unit including an inlet and an outlet; a nosepiece unit including a nosepiece for fitting to a nasal cavity of the subject and being in fluid communication with the outlet of the substance supply unit; and a mouthpiece unit including a mouthpiece in fluid communication with the inlet of the substance supply unit through which the subject in use exhales such as to entrain substance from the substance supply unit and deliver the same through the nosepiece; at least one temperature modifier for reducing a temperature of the exhaled air flow such as to reduce the absolute humidity thereof; characterized by: the substance supply unit comprising a container chamber for receiving a substance-containing container which contains a dose of substance; the container chamber and the nosepiece comprising a unitary, replaceable component; the at least one temperature modifier comprising a plurality of elongate channels; the plurality of elongate channels allowing a flow therethrough at a flow rate of at least about 10 l/min at a pressure of less than about 2 kPa; and the plurality of elongate channels providing a pressure drop of not more than about 0.5 kPa to the exhaled air flow. the substance supply unit comprising a container chamber for receiving a substance-containing container which contains a dose of substance; the container chamber and the nosepiece comprising a unitary, replaceable component; the at least one temperature modifier comprising a plurality of elongate channels; the plurality of elongate channels allowing a flow therethrough at a flow rate of at least about 10 l/min at a pressure of less than about 2 kPa; and the plurality of elongate channels providing a pressure drop of not more than about 0.5 kPa to the exhaled air flow.