When an average projector operates, it produces a lot of heat. To ensure the lamp operates efficiently, the heat must be removed. Projectors have fans that force air around the various components. The fans are useful, but the air generally has dust and various particles, so the air must be filtered. When the air is not filtered, the dust will build around the components, and it will insulate the projector. Insulation keeps the heat in the device, and this will damage the lamp. Proper maintenance of the filters, however, prevents this problem; filter damage is not covered by the warranty.