Home Improvement

I have a centrally located dual flue chimney that serves both two wood stoves and an oil furnace. In the basement there are galvanized steel clean out doors for each flue. When I run the kitchen exhaust, a bathroom exhaust, the dryer, or the central vacuum the basement starts to smell like creosote right around the clean out doors.

I assume the issue is the house is too air tight and the chimney clean outs happen to be the easiest draft entry. Question is, what do I do about it? Should I seal up the clean out doors tighter before I use the wood stoves this winter?