A cleaning machine comprising: a housing; a fluid distributor configured to dispense fluid; a supply tank coupled to the housing and configured to supply fluid to the fluid distributor; a suction nozzle configured to engage a surface to be cleaned; a suction source within the housing and in fluid communication with the suction nozzle, the suction source operable to draw fluid into the suction nozzle from the surface to be cleaned; a recovery tank selectively mounted on the housing and in fluid communication with the suction nozzle and the suction source, the recovery tank configured to store fluid drawn through the suction nozzle, the recovery tank including a container having a bottom wall and sidewalls projecting upwardly from the bottom wall thereby defining an open top, a cover coupled to the open top of the container, and characterized in that it further comprises an air-liquid separator extending into the recovery tank from the open top, the air-liquid separator having a vertical sidewall, a lower wall extending laterally from the lower end of the vertical sidewall toward an adjacent sidewall of the sidewalls of the container, wherein the vertical sidewall, the lower wall, and the adjacent sidewall define a separation chamber, wherein the vertical sidewall includes a rib extending outwardly from the vertical sidewall and into the separation chamber, wherein the separation chamber includes a dirty fluid inlet receiving fluid from the suction nozzle through the cover, a first dirty fluid outlet directing fluid from the separation chamber into the container, and a second dirty fluid outlet directing fluid from the separation chamber into the container, the rib positioned between the first dirty fluid outlet and the second dirty fluid outlet. a housing; a fluid distributor configured to dispense fluid; a supply tank coupled to the housing and configured to supply fluid to the fluid distributor; a suction nozzle configured to engage a surface to be cleaned; a suction source within the housing and in fluid communication with the suction nozzle, the suction source operable to draw fluid into the suction nozzle from the surface to be cleaned; a recovery tank selectively mounted on the housing and in fluid communication with the suction nozzle and the suction source, the recovery tank configured to store fluid drawn through the suction nozzle, the recovery tank including a container having a bottom wall and sidewalls projecting upwardly from the bottom wall thereby defining an open top, a cover coupled to the open top of the container, and characterized in that it further comprises an air-liquid separator extending into the recovery tank from the open top, the air-liquid separator having a vertical sidewall, a lower wall extending laterally from the lower end of the vertical sidewall toward an adjacent sidewall of the sidewalls of the container, wherein the vertical sidewall, the lower wall, and the adjacent sidewall define a separation chamber, wherein the vertical sidewall includes a rib extending outwardly from the vertical sidewall and into the separation chamber, wherein the separation chamber includes a dirty fluid inlet receiving fluid from the suction nozzle through the cover, a first dirty fluid outlet directing fluid from the separation chamber into the container, and a second dirty fluid outlet directing fluid from the separation chamber into the container, the rib positioned between the first dirty fluid outlet and the second dirty fluid outlet.