Just downloaded the owners manual for mine. It states...
Vacuuming Liquids
IMPORTANT:
1. When picking up small amounts of liquid the filter may be left in place.
2. When picking up large amounts of liquid we recommend that the filter be removed. If the filter is not removed, it will become saturated and misting may appear in the exhaust.
3. After using the vac to pick up liquids, the filter must be dried to reduce the risk of possible mildew and damage to the filter.
4. When the liquid in the drum reaches a predetermined level, the float mechanism will rise automatically to cut off air-flow.
When this happens, turn off the vac, unplug the power cord, and empty the drum. You will know that the float has risen because vac airflow ceases and the motor noise will become higher in pitch, due to increased motor speed.