Ignis Ventless Bio Ethanol Fireplace Optimum with Safety Glass Ventless - no chimney, no gas or electric lines required. Easy or no maintenance required. Easy Installation - Can be mounted directly on the wall or recessed. Capacity: 1.5 Liters per Burner. Approximate burn time - 5 - 9 hours per Burner per refill. Approximate BTU output - 6000 per Burner (Total BTU - 18000).