A room ventilation system with a ventilation device and at least two ventilation device air ducting components , wherein the ventilation device has a device housing , in which at least one filter element , at least one heat recovery unit and at least one fan unit are accommodated, wherein the device housing has at least one device coupling side (3; 3a, 3b) with at least two coupling connections , and wherein a respective coupling connection of the ventilation device is fluidically connected to a device connection opening , wherein a respective ventilation device air ducting component has a base body with a plurality of lateral surfaces that delimit an interior space of the base body , wherein the device connection opening is formed on a first lateral surface of the base body , wherein a first connection opening is formed on a second lateral surface of the base body , and wherein the first lateral surface is arranged opposite of the second lateral surface and the device connection opening therefore is arranged opposite of the first connection opening , characterized in that a second connection opening is formed on a third lateral surface of the base body , wherein the third lateral surface connects the first lateral surface to the second lateral surface , wherein a closure device is fastened on the base body , and wherein the closure device either is arranged so as to close the first connection opening in a sealing manner such that the device connection opening is fluidically connected to the second connection opening via the interior space or arranged so as to close the second connection opening in a sealing manner such that the device connection opening is fluidically connected to the first connection opening via the interior space . wherein the ventilation device has a device housing , in which at least one filter element , at least one heat recovery unit and at least one fan unit are accommodated, wherein the device housing has at least one device coupling side (3; 3a, 3b) with at least two coupling connections , and wherein a respective coupling connection of the ventilation device is fluidically connected to a device connection opening , wherein a respective ventilation device air ducting component has a base body with a plurality of lateral surfaces that delimit an interior space of the base body , wherein the device connection opening is formed on a first lateral surface of the base body , wherein a first connection opening is formed on a second lateral surface of the base body , and wherein the first lateral surface is arranged opposite of the second lateral surface and the device connection opening therefore is arranged opposite of the first connection opening , characterized in that a second connection opening is formed on a third lateral surface of the base body , wherein the third lateral surface connects the first lateral surface to the second lateral surface , wherein a closure device is fastened on the base body , and wherein the closure device either is arranged so as to close the first connection opening in a sealing manner such that the device connection opening is fluidically connected to the second connection opening via the interior space or arranged so as to close the second connection opening in a sealing manner such that the device connection opening is fluidically connected to the first connection opening via the interior space . <EOS>