The pre-filters in the FA-430 will need to be replaced when 80% of the pre-filter is clogged or when it was used for 160 hours. The orange lamp will flash when the pre-filter replacement is needed. After the pre-filter has been replaced 10 times and the current pre-filter is 80% clogged or has been used for 160 hours, the main filter will need to be replaced. The orange and red lamp will flash when the main filter replacement is needed.