Panasonic FV-20NLF1 240 CFM In-Line Fan. Panasonic FV-20NLF1 240 CFM In-Line Fan is a ventilation fan manufactured by Panasonic for the use in residential bathrooms. The fan boasts a CFM (cubic feet per minute) rating of 240 which gives it the ability to work well with in a medium to large size bathroom. The in-line fan offers a 4 inch duct diameter which allows for an easy installation for truss or joint attachments. The fan comes with suppension brackets and other brackets in order to attach the fan easily to a 2 x 4 construction or larger. This Panasonic fan is part of the WhisperLine models which promote a super quiet operation.