The clean out door is designed to allow homeowners to remove ash from fireplaces at the exterior side of a wood burning masonry fireplace. During the chimney sweep and cleaning process, our technicians DO NOT CLEAN or empty this debris filled cavity. This is the responsibility of the home owner. What our cleaning process entails is the cleaning of the chimney liner, smoke chamber, damper shelf and the firebox debris. The material we remove during our cleaning is creosote which is highly flammable and is a fire hazard. The ash in the ash dump is burnt ash which is not flammable. Most chimney sweeps as general practice do not clean these ash dumps. We only clean upon request and may be at an additional cost.

The clean out door for a furnace is designed to allow a chimney sweep to sweep the flue and remove the creosote deposits after cleaning. The furnace clean out  for a furnace is always cleaned during service and is required by IRC building codes. 

Both look alike but are two different uses.