Gas burning fireplaces come in two different styles, vented and vent free. It is important to know which one you have before choosing a fireplace log. Vent free fireplaces use either refractory or ceramic logs. These two types of logs have some differences that you should consider so as to choose the right one for your fireplace.

Gas burning fireplaces come in vented and vent free styles.

How Vent Free Logs Work

Both refractory and ceramic logs have a burner specifically designed to burn gas cleanly while producing almost no exhaust. This eliminates the need for an open damper. As a result, 99.9 percent of the heat produced goes straight into the room. Vent free logs require a lower flame to avoid as much contact as possible with the logs. A flame constantly in contact with the log will produce soot and exhaust gases.

Construction Materials

Refractory logs are made of a heat resistant concrete and are designed to mimic actual wood logs. They come in a variety of shapes, styles and colors. Ceramic logs are made of either molded ceramic fibers or extruded bisque ceramic clay. Like refractory logs, they come in various designs. Ceramic logs are designed to produce a warm glow after about 15 minutes of use.

Cost and Considerations

Refractory logs are usually the least expensive and can be found at most major retail chains, home centers and discount stores. Ceramic logs typically cost more and are usually only found at specialty stores. Refractory logs weigh about 75 percent more than ceramic logs, and depending on the manufacturer can last longer. Poorly manufactured refractory logs can start to crumple and crack within a short period of time. Ceramic logs weigh significantly less and resist extreme temperature variations much better than refractory logs. Due to the manufacturing process, ceramic logs are not as intricately designed as refractory logs and the heat resistant paint tends to fade and wear quicker.


Vent free logs come with a built-in carbon monoxide sensor that will alert you when carbon monoxide levels are rising. A built-in oxygen detection safety pilot will automatically shut the fireplace off when oxygen levels are too low. A biproduct of clean burning gas is water, which can result in a buildup of moisture in the home, leading to mold and mildew, so proper home ventilation is necessary. Vent free logs are not designed to burn all day. Read the manufacturer's directions to determine how long a particular log can safely burn.