A projectors air filter prevents dust from accumulating on the optical elements inside the projector. The air filter plays a crucial role in preventing dust accumulation on the projector's optical components. Should the filter become clogged with dust particles it will reduce the cooling fans’ effectiveness and will result in internal heat buildup, adversely affecting the life of the projector. If you are replacing your lamp, it is a good time to replace your filter. Manufacturers suggest replacing the filter when changing the lamp to ensure optimal performance. Many projectors have a filter warning icon or message that will appear on the screen, when this occurs replace the filter immediately. If you do not have a filter warning icon or message, or simply are not sure, remove the filter and inspect it visually. If there is any buildup, it is too much! Protect your projector and bulb life by regularly changing filters as well as by keeping the projector free from overall dust and debris.