Eventually, when the iron exhausts most of its heat energy, the air in the hut ceases to be warmed by it and will start cooling.
(the iron; exhausts; most of its heat energy) (the air in the hut; to be warmed; by it) (the air in the hut; will start; cooling; T:when the iron exhausts most of its heat energy)
the iron the air in the hut the air in the hut
exhausts to be warmed will start
most of its heat energy
by it
cooling T:when the iron exhausts most of its heat energy