LG BX27C-SL Owner's Manual page 44

Setting
Cooling fast
There are the following options in the cooling fans operation when the projector is turned off.
ON ... Faster and louder-sound than the normal operation, but it takes less time than off option.
OFF... Normal operation with about 60 seconds cooling times.
High land
This projector provides Fan control function in the "Setting" menu. Choose the running speed of cooling fans
from the following options according to the ground elevation where you use the projector.
Off......Normal speed.Set this function to "Off " when using the projector in non-high altitude environment.
On......Faster than Off mode.Select this mode when using the projector in high altitudes (above 2000m) where
the fans are weak in cooling effect.
Filter Counter
This function is used to set a frequency for the filter cleaning.
When the projector reached a specified time between cleanings, a Filter warning icon appears on the screen,
notifying the cleaning is necessary. After cleaning the filter, be sure to select RESET and set the timer. The Filter
warning icon will not turn off until the filter counter is reset.
Filter counter: The time of filter using after last cleaning.
Timer: The time between cleanings,100 hours,200 hours,300 hours.
Filter counter reset: Reset the filter counter.
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Filter warning icon