Air purifiers generally require maintenance every three to six months to maintain optimum efficiency. Those with permanent filters or collection plates usually require more frequent cleaning, while disposable HEPA filters usually last between six to 12 months. Many models incorporate a timer or sensor to indicate cleaning is needed.
Ionizer-style air purifiers typically utilize reusable charged plates inside the unit that attract contaminants. These plates become dirty over time and, depending on the amount of allergens in the home, should be cleaned at least once a month.
Air purifiers that use physical filters typically require replacement instead of cleaning. Once the filter media becomes clogged with dust, it loses its ability to remove contaminants. In addition to the main filter's lifespan, which varies from manufacturer to manufacturer, some units employ carbon pre-filters that need replacement every three to six months.