If they are near the cold air return that s all that will happen is you cycle warm air into the cold air return.
Cold air return basement ceiling.
This tool promotes cool air circulation through duct work and other house passageways.
The air flows across the ceiling in the hallway towards a larger cold air return that does extend to the basement furnace.
You do this and i guarantee you that the second floor is going to be much more comfortable year round.
Have a professional contractor install a cold air return gadget in your basement.
This pulls the air across your body.
The return air vent openings need to be on the opposite side of the room so the conditioned air is pulled across the room.
In the upper stories of the house the return air duct openings on each floor should be approximately equal to the sum of the hot air outlets.
If there is a cold air return on the floor the warm air that would normally tend to collect near the ceiling will be sucked down into the furnace.
In the basement to avoid chimney backdrafting the return air duct should be only half as large as the sum of the hot air ducts.
If the supply ducts are in the floor then the return air should be located up high.
By putting the cold air return on the floor it will vacuum up the cold air on the floor and draw down the warm air from the ceiling.
The basement one should be on the floor not the ceiling of the basement.
One other caution is to have the cold air.