Abstract: An air filter assembly and use thereof for filtration of air in wet or damp conditions, said air filter assembly comprising: an air filter comprising a front frame defining at least one rectangular aperture for receiving an air flow to be filtered; characterized in that said air filter assembly comprises a deflector element extending alongside edge portion of the rectangular aperture and adapted an to deflect an air flow passing through the rectangular aperture away from an adjacent inside surface of the air filter; and a liquid drain arranged such that liquid collected at said adjacent inside surface of the air filter can exit the air filter through said liquid drain.