http://www.westcountryfires.co.uk/fires/products/382.asp

It's a flueless gas fire. In other words, all of the carbon dioxide it
produces will remain in the room, instead of going up the chimney to
draw in fresh air from outside.

"the fire has the ability to burn off the odorous and stale air in the
room and efficiently return warm and neutral air back into your
airspace"

Wow.

Daniele