When shopping for gas logs, you'll need to choose vented or vent-free logs. This decision comes down to many factors, including looks versus efficiency, local building codes and fireplace placement.
With vented logs, you'll enjoy a large, realistic-looking flame that operates with an open chimney flue or damper. These logs, which simulate a wood-burning fire, are more decorative than they're an efficient heat source because much of the generated heat goes up the chimney.
Vent-free logs, which operate with the chimney flue closed, won't give you that roaring fire effect. The flame isn't as realistic or as high as you'll find with vented logs. But they are an efficient heat source - 100% of the heat generated stays in your home. You'll often see vent-free logs referred to as vent-free heaters because that's essentially what they are. Most sets have a thermostatic control that helps maintain a consistent room temperature. Vent-free heaters add moisture to the air, so it's important to install them in a room with proper ventilation to avoid formation of mildew.
Vent-free heaters aren't permitted in bedrooms, bathrooms or recreational vehicles, and must be installed in an area where curtains, furniture, clothing or other flammable objects are at least 36 inches away from the perimeter of the heater. Vent-free heater installation isn't recommended in high-traffic, windy or drafty areas.