Fewer air cleaning units utilize a static-charged collection grid, which has one of the longest pre-filter lifetimes. These static grids work very well but are commonly a lot more expensive than the other types of pre-filters, which makes them less desirable.
Some air purifiers even utilize specialized pre-filters which may include activated carbon, which can be an invaluable extra. However, the drawback to some of these filters is that they may, in fact, need replaced.
This can result in an added expense, which may be a drawback to such a design. However, there are many air purifiers on the market which have a separate pre-filter and carbon filters. This means that you can have the best of both worlds, namely a washable pre-filter that won’t need to be replaced, in addition to a separate carbon filter.