What happends if in that is no filter within a house furnace? ...
Answers: The filter is to filter out dust and particals in the intake nouns...what will happen is that dust will build up on the lover & coils, this isn't good because it lowers the effecance of the component and it puts dust into your home.....you really need them contained by and changed on a regular bases....
The dirt and dust will acquire into the duct work and into the house, could cause allergic reaction