A leakage valve for use in a patient ventilation system, comprising a valve housing consisting of a first and a second housing part and preferably made of plastics material, wherein the two housing parts (2, 3) form a preferably circular fluid channel in cross-section, wherein the valve housing comprises the following: a first connection piece on the first housing part, a second connection piece on the second housing part and a radially outwardly projecting housing region between the two connection pieces (4, 5), at least one through-opening, which is arranged approximately at the height of the outwardly projecting housing region and allows or allow for the discharge of a fluid out of the fluid channel in the form of a leakage flow, a leakage channel for discharging the leakage flow out of the leakage valve, which leakage channel is also arranged approximately at the height of the outwardly projecting housing region, which extends around at least some and preferably the entire circumference of the valve housing, and which is preferably formed by means of the two housing parts (2, 3), a locking mechanism, by means of which the two housing parts (2, 3) can be connected to one another, wherein at least one, preferably multiple latching tab(s) are provided as the locking mechanism, which are curved according to the inner radius of the connection piece (4 or 5), and which comprise a front nose, and which, in the locking state, extend along the inside of the connection piece (4 or 5) and engage with their nose in the outer front face of the connection piece (4 or 5) and ensure axial locking, and wall regions are provided between the latching tabs, which wall regions are curved according to the inner radius of the connection piece (4 or 5) and which adjoin the inner surface of the connection piece (4 or 5), wherein the two housing parts (2, 3) can be rotated relative to one another in the locked state, multiple radially extending webs are provided on the second housing part around the circumference, between which webs the through-openings are provided or which webs laterally delimit the through-openings, the webs project outwards beyond the curved wall regions, and there is a circumferential annular space between the inner wall of the extended housing region and the outer end of the relevant web. a first connection piece on the first housing part, a second connection piece on the second housing part and a radially outwardly projecting housing region between the two connection pieces (4, 5), at least one through-opening, which is arranged approximately at the height of the outwardly projecting housing region and allows or allow for the discharge of a fluid out of the fluid channel in the form of a leakage flow, a leakage channel for discharging the leakage flow out of the leakage valve, which leakage channel is also arranged approximately at the height of the outwardly projecting housing region, which extends around at least some and preferably the entire circumference of the valve housing, and which is preferably formed by means of the two housing parts (2, 3), a locking mechanism, by means of which the two housing parts (2, 3) can be connected to one another, wherein at least one, preferably multiple latching tab(s) are provided as the locking mechanism, which are curved according to the inner radius of the connection piece (4 or 5), and which comprise a front nose, and which, in the locking state, extend along the inside of the connection piece (4 or 5) and engage with their nose in the outer front face of the connection piece (4 or 5) and ensure axial locking, and wall regions are provided between the latching tabs, which wall regions are curved according to the inner radius of the connection piece (4 or 5) and which adjoin the inner surface of the connection piece (4 or 5), wherein the two housing parts (2, 3) can be rotated relative to one another in the locked state, multiple radially extending webs are provided on the second housing part around the circumference, between which webs the through-openings are provided or which webs laterally delimit the through-openings, the webs project outwards beyond the curved wall regions, and there is a circumferential annular space between the inner wall of the extended housing region and the outer end of the relevant web.