If you have a fireplace that has a set of glass doors you have probably notices the vents both above and below the glass doors. Those vents are there to allow the fireplace to intake air and output heat.
These can also be present in direct vent fireplaces that have a sealed glass display. If you need to cover those vents up you can use vent covers made by Christy Walker Creations. They come in black and gold variety to match your fireplace decor.