Do you have a CO detector in the basement? I would be willing to bet that if you keep that ash pan door open and the damper fully closed that your going to see elevated level of CO showing up and thats NOT good. This is the reason that ,from all of the research I have done in the past, there ARE no REAL stoves that burn Coal and Wood BOTH properly. A coal fire requires different draft and air flow to properly burn than a wood fire does. There are currently NO EPA certified stoves that burn both because of this required design difference. If you want to do a short experiment get a GOOD CO detector and put it in the basement then do a test burn during the day when everyone is awake ect...close off those vents in the floor and watch that CO detector (make sure you get one with a digital readout...not just an alarm) just make sure that your not standing there the whole time because if there IS elevated CO then you could passout without much of a warning. Make sure all of the basement doors and windows are shut just as they would be normally...start the burn and check the CO in maybe 30 min or an hour...and do it QUICK...if the CO is elevated close the ash door open the damper and basement door or windows and get OUT of there.