Forced hot air heating: 有可能只1间屋子吹冷风吗？

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.  请有经验的大师指点。

多谢了。