How do you know if your gas fireplace is vented?

The fireplace needs to be turned on. If the flames reach above the gas logs and the look like a wood burning fireplace, then the logs must be vented. The fireplace is vent-free if the flames are small.Turn on the fireplace. If the flames come on the gas logs and look like a wood fireplace, then the logs must be ventilated. If the flames are small, one has a blue mold, the fireplace is without ventilation.