How to Use an Inline Exhaust Fan to Vent More Than One Bathroom First, install plastic exhaust grills in each bathroom ceiling. Run 4-in. flexible ductwork from the grills to the inline fan.

Inline exhaust fans are placed in line with existing ductwork ... which can also be very helpful when it comes to installation. It’s available in 4- and 8-inch models as well, so you should ...