This morning I was walking past the return vent in my house, and I felt HOT AIR coming out of it. This has never happened before in the ten years that I have lived there, and no heat is coming out of any of the actual vents, only the return vent. I'm no HVAC contractor, but I don't think anything is suppose to come out of the return vent at all. This is REALLY starting to concern me, especially considering that the thermostat is TURNED OFF! What in blue blazes is going on??? If anyone can tell me what is going on, PLEASE TELL ME!!! Thanks.