I have 2 bathrooms and a kitchen that are currently unvented. I would like to install an inline exhaust fan to service all three. I will be putting the exhaust fan just inside a gable that will have an exhaust port to the outside. Are there any issues with having a kitchen and bathroom share exhaust ducting? They will all have dampers at the intake vent. See picture for diagram. I have already calcuated the CFM needed for the kitchen which will be about 360 CFM and will be getting an appropriate fan. Are there any issues, safety or otherwise, with the sharing of the ductwork? Grease buildup?
Chapter 4 says you cannot use the same ducting for ventilation, as you do for your range exhaust. Chapter 5 is quite explicit in what materials should be used for the range exhaust ducting, and also says that the ducting cannot be shared. If you're using the ventilation ducting between two or more spaces, you'll have to be sure the fan and ducting are both adequate to move the amount of air required. you'll also have to insure there is an adequate supply of makeup air.
NOTE: Local codes may vary. Contact your local government for all applicable codes.