Forced hot air heating: 有可能隻1間屋子吹冷風嗎？

Tenant said the furnace is blowing cold air in ding room.  I think dining room is on a slab, half basement is under living room and that is where the furnace is.

I asked several contractors,they said it is impsossible.  But one guy also said maybe I should check the duck to see if it is leaking or disconnected.  請有經驗的大師指點。

多謝了。