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. <EOS>