Blood treatment device for use in blood treatment therapies, comprising: an extracorporeal blood circuit, a dialyzer and a dialysis fluid circuit, wherein the extracorporeal blood circuit and the dialysis fluid circuit are separated from each other via a membrane provided in the dialyzer, via which blood can be filtered, and the extracorporeal blood circuit has an arterial portion upstream of the dialyzer and a venous portion downstream of the dialyzer; an air detector arranged in the venous portion and configured to continuously monitor whether air is present in the venous portion; a plurality of pumps (20, 36, 46, 56), including at least one blood pump which is a pump in the arterial portion and is configured to pump blood through the extracorporeal blood circuit; a venous hose clamp, which is a hose clamp in the venous portion and is configured to selectively clamp or release the venous portion; a user interface comprising a display with a touch screen; and a control unit, which is configured, when it receives information from the air detector that there is air in the venous portion, to stop the blood pump, to close the venous hose clamp, to raise an alarm, and to display on the display a venous air removal window displaying instructions to a user for removing the air in the venous portion and displaying status reports about the removal of the air; and to carry out an automatic removal of air from the venous portion on a user-initiated basis, characterized in that a manually actuatable clamp is provided in the venous portion in addition to the venous hose clamp, by means of which a user can selectively clamp or release the venous portion. an extracorporeal blood circuit, a dialyzer and a dialysis fluid circuit, wherein the extracorporeal blood circuit and the dialysis fluid circuit are separated from each other via a membrane provided in the dialyzer, via which blood can be filtered, and the extracorporeal blood circuit has an arterial portion upstream of the dialyzer and a venous portion downstream of the dialyzer; an air detector arranged in the venous portion and configured to continuously monitor whether air is present in the venous portion; a plurality of pumps (20, 36, 46, 56), including at least one blood pump which is a pump in the arterial portion and is configured to pump blood through the extracorporeal blood circuit; a venous hose clamp, which is a hose clamp in the venous portion and is configured to selectively clamp or release the venous portion; a user interface comprising a display with a touch screen; and a control unit, which is configured, when it receives information from the air detector that there is air in the venous portion, to stop the blood pump, to close the venous hose clamp, to raise an alarm, and to display on the display a venous air removal window displaying instructions to a user for removing the air in the venous portion and displaying status reports about the removal of the air; and to carry out an automatic removal of air from the venous portion on a user-initiated basis, characterized in that a manually actuatable clamp is provided in the venous portion in addition to the venous hose clamp, by means of which a user can selectively clamp or release the venous portion.