Gas logs are available for vented and vent free applications. Vented gas logs by design have a realistic flame presentation. They have a higher BTU input (gas volume) than vent free logs, which provides a stronger flame. Because the combustion is released through a vented flue system, the flames can wrap around the logs in a more realistic pattern. Ventless gas fireplace logs are approved to burn without a venting system. This technology by design is a high efficiency heating product for your unit.