an animal shed having an animal shed floor with a first and a second surface spaced apart, such that the floor has a thickness different from zero, and multiple flow holes extending from the first to the second surface;

a reservoir situated under the animal shed floor, wherein the flow holes open up to the reservoir, and the flow holes allow a fluid flow, including a urine flow, from the animal shed to the reservoir, wherein feces stays on the first surface;

a floor opening in the animal shed floor to allow manure to be dumped in the reservoir;

a manure-removal vehicle for removing manure from the animal-shed floor and dumping the manure into the reservoir at the floor opening;

an air extraction device for extracting air underneath the floor, out of the reservoir; and

a device extending from the floor opening into the reservoir, wherein the device is configured to prevent an airflow from the animal shed to the reservoir through the floor opening when in use,

wherein the device comprises a tube extending from the floor at the floor opening, and towards a bottom of the reservoir,

wherein the tube has a free end ending at a distance different from zero from a bottom of the reservoir, the tube having a base that closes off the free end, and forms a container with a peripheral sidewall that encloses an interior of the device,

wherein the peripheral sidewall comprises an outlet opening towards the reservoir, the outlet opening being located at a distance from zero from the base,

wherein the device further comprises a cover extending into the tube and covering the outlet opening and part of the base,

wherein an end edge of the cover is at least at a same height as a lower edge of the outlet opening, the lower edge being at a distance different from zero from the base, thereby creating a passage from the floor opening to the outlet opening, and

wherein in use the airflow from the animal shed to the reservoir is prevented when a manure or feces level in the tube is at least at a similar height as the end edge of the cover or higher, thereby blocking the passageway for the airflow.