Question: We are thinking of installing a wood or gas stove insert in our existing fireplace in a 70 year old house. There is an ash clean out trap door (about 4in x 6in) in the center of the existing fireplace floor. The ash duct ends in the basement at the base of the chimney a foot or two off the floor. Is it likely that we could route an outside air intake for an insert through this ash cleanout? Difficult- but not impossible for a wood insert- probably impossible for a gas insert or stove The base of the existing cleanout could be ducted to a vent in the basement wall or through a window similar to a dryer vent or perhaps it could just draw from the basement (as the boiler does). This would reduce the amount of cold outside air drawn into the living space through windows and other leaks. Any experience with such a setup or specific products that could be ducted for outside air this way Answer: Wood inserts use only a small amount of room air .... some do have outside air hookups- but are not easy to fiddle within the confines of a fireplace. Gas Inserts use quite a bit of room air- but to my knowledge- they so not have or recommend outside air hookups. <p> Newer gas inserts use a two pipe system called "Direct vent" which brings outside air in using one pipe and exhausts gases out the other.