it's really cold outside,so I decided to throw a scoop of coal in with the wood, it seems to help make the burn time longer, but last night it caused a problem on the coldest night of the season. the coal plugged the nozzle so the eko couldn't gasifie ,woke up to a 50 degree house. the storage tank was down to 120 degrees.not sure i'm going to play with the coal again without my backup heat working.