Kitchen Exhaust in Bathrooms

Ritu Gandhi has a smelly problem in Madison, WI. Here it is:

"We have a kitchen exhaust fan over our cooking range but every time we turn it on food smells seem to come into our bathrooms (upstairs) and in the basement. We do have an air to air exchanger. The kitchen exhaust does seem to have venting to the outside. Any idea why this is happening and what we can do to eliminate the cooking smells in out bathrooms?"

Here's my answer:

Ritu, have you checked to see if the exhaust ducts are interconnected?

You're never supposed to do that unless you have a central fan in the attic that vacuums air from the rooms and then exhausts it out to the outside of your home.

If you have fans in the kitchen and bathrooms that PUSH air through the exhaust piping and the pipes are interconnected, the path of least resistance for the air to leave the piping may be another room instead of the outside vent hood!