The 6K.J2K11.001 Dust Filter for the BenQ W500 LCD Projector requires cleaning every 1000 hours use. You can use the Advanced Setup > Dust Filter > Dust Filter Hours menu or the Information menu to check how long the filter has been used.
If the filter is not cleaned, it can become clogged with dust and prevent proper ventilation. This can cause over-heating and a malfunction of the projector. The projector will display a warning message if the filter is seriously clogged with dirt. The filter should be replaced if it is broken or if dirt is difficult to remove.