An ideal air purifier should effectively remove a wide range of airborne pollutants, including dust, pollen, pet dander, and harmful particles. It should feature a multi-stage filtration system, typically including a pre-filter, activated carbon filter, and a True HEPA filter. The unit should be energy-efficient, with adjustable fan speeds and an auto mode that responds to air quality changes. Quiet operation, especially in sleep mode, is crucial for bedroom use. Additional features like air quality indicators, filter replacement reminders, and coverage area appropriate for the intended space contribute to the overall effectiveness and user experience.