How do you clean the air filter in a lawnmower Not even sure where it is?

Its next to the carborator it could be round or square if its a new model its mage out of sponge and you can rinse it clean with water then add a little motor oil to it to help colect dirt> If its an older model it could be made on paper in that case you can blow it clean with air or lightly bang it clean but the paper ones should be replaced when dirty