noun
paper-covered frame to prolong fire
A traditional device placed over a hearth or brazier to make the fire last longer. Rare, historical term; mostly encountered in descriptions of old Japanese household items.
昔の家では、火鉢の上に助炭をかぶせて火を長持ちさせた。
In old houses, they placed a 助炭 over the brazier to make the fire last longer.