RabbitFighter

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?

I recently got a deal on a never used power broom attachment for an interchangeable trimmer tool system. Problem is, it's Husqvarna and has a (to me) unusual hex drive shaft while all the power heads I own have square shaft drives. The outer shafts are the same size and should work if I can adapt the drive shaft coupler. Before I start planning to make my own adapter does anyone know of off the shelf adapters for this purpose? Seems like there's a market for adapting different systems.