Zeolite 3A is typically used for drying gases and liquids due to its small pore size, which allows it to adsorb moisture while preventing larger molecules like nitrogen and oxygen from entering. Therefore, 3A zeolite is not commonly used for oxygen concentration, as its primary role is dehydration rather than nitrogen adsorption. Zeolite types like 13X or LiX are better suited for oxygen concentrators, as they have larger pore sizes and are designed to adsorb nitrogen effectively.