Vented or Vent ree gas log sets?

I have two friends that have masonry wood burning fireplaces with gas log sets installed in them. How can you tell the difference between log sets that need to be vented and those that do not? both sets have piezo electric ignitors on them and pilot lights if that makes any difference.

The rating plate attached to them. If there is not one assume it is vented, and technically if there is not one it should not even be in use.

Also you can tell by the pilot, the Vent Free will have an ODS (Oxygen Depletion Sensor). Yes, when the oxygen in the room is depleted to a certain level it shuts down the fireplace (before you die).

Here is a random picture I found online: http://www.fastfireplaces.com/ods-pilot-assembly-vent-free.html
http://www.fastfireplaces.com/media/catalog/product/o/d/odsmanual-ng_1.gif

Here is what a vented gas log pilot might look like:
http://www.fastfireplaces.com/media/catalog/product/s/a/safetypilot.jpg