A breather for a reservoir, said breather comprising: a housing; a first opening in the housing configured to be in fluid communication with air outside of the reservoir; a second opening in the housing configured to be in fluid communication with air inside of the reservoir; desiccant positioned within the housing such that air passing through the breather from the outside to the inside of the reservoir must pass through the desiccant; and a humidity sensor (102; 302) positioned within the housing, wherein the humidity sensor is operable to provide a humidity signal indicative of a humidity level adjacent the humidity sensor, characterised: by a controller electrically connected to the humidity sensor, wherein the controller is operable to determine an end of life condition of the breather as a function of the humidity signal from the humidity sensor, and in that in use, the humidity level decreases after initial installation of the breather on the reservoir and the controller is configured to: ignore the humidity signal until the humidity signal indicates that the humidity level adjacent the humidity sensor (102; 302) has decreased below a predetermined maximum humidity level; or ignore the humidity signal for a predetermined period of time after initial installation of the breather on the reservoir, wherein initial installation of the breather on the reservoir comprises providing power to the controller. a housing; a first opening in the housing configured to be in fluid communication with air outside of the reservoir; a second opening in the housing configured to be in fluid communication with air inside of the reservoir; desiccant positioned within the housing such that air passing through the breather from the outside to the inside of the reservoir must pass through the desiccant; and a humidity sensor (102; 302) positioned within the housing, wherein the humidity sensor is operable to provide a humidity signal indicative of a humidity level adjacent the humidity sensor, characterised: by a controller electrically connected to the humidity sensor, wherein the controller is operable to determine an end of life condition of the breather as a function of the humidity signal from the humidity sensor, and in that in use, the humidity level decreases after initial installation of the breather on the reservoir and the controller is configured to: ignore the humidity signal until the humidity signal indicates that the humidity level adjacent the humidity sensor (102; 302) has decreased below a predetermined maximum humidity level; or ignore the humidity signal for a predetermined period of time after initial installation of the breather on the reservoir, wherein initial installation of the breather on the reservoir comprises providing power to the controller. by a controller electrically connected to the humidity sensor, wherein the controller is operable to determine an end of life condition of the breather as a function of the humidity signal from the humidity sensor, and in that in use, the humidity level decreases after initial installation of the breather on the reservoir and the controller is configured to: ignore the humidity signal until the humidity signal indicates that the humidity level adjacent the humidity sensor (102; 302) has decreased below a predetermined maximum humidity level; or ignore the humidity signal for a predetermined period of time after initial installation of the breather on the reservoir, wherein initial installation of the breather on the reservoir comprises providing power to the controller. ignore the humidity signal until the humidity signal indicates that the humidity level adjacent the humidity sensor (102; 302) has decreased below a predetermined maximum humidity level; or ignore the humidity signal for a predetermined period of time after initial installation of the breather on the reservoir, wherein initial installation of the breather on the reservoir comprises providing power to the controller.