The MU05842 Hitachi Projector Air Filter prevents dust from building up on the optical elements of your projector unit. It plays a critical role in preventing dust accumulation. If the air filter becomes clogged it will result in higher operating temperatures because of reduced air flow.  This could ultimately reduce the lamp life of your projector. If you are replacing your Hitachi Projector Lamp, it is also a good idea to replace your filter. Manufacturers suggest replacing the filter when changing the lamp to ensure optimal performance.   Increase the life of your lamp and projector by changing out your air filter on a regular basis.