This is the 6517th most frequent Korean word.
열기가
"열기가" means "heat" or "enthusiasm."
열기 refers to the heat or high temperature in the room.
지금 이 방은 너무 더워서 열기가 느껴져요.
Right now, this room is so hot that I can feel the heat.
열기 is used metaphorically to describe the passionate atmosphere.
그 콘서트의 열기가 대단했어요.
The enthusiasm at that concert was amazing.
열기 here relates to the energy or excitement in the environment.