Operation

The throat damper in the chimney is normally opened and closed through the operation of a lever that is located either to the side of the fireplace or out of sight just above the firebox. You may have to get down on your hands and knees and peer up the chimney to locate the lever if you have not operated your lower damper before. A flashlight may help you to see the damper lever. A damper that has not been operated for some time may be stiff, so be prepared to exert a little pressure if it does not move easily. The lever may slide from side to side, or it may move in an up and down motion, depending on the manufacturer. Always make sure the damper is open before lighting the fire for the first time, and close the damper completely when you stop using the fireplace during the summer months.

Advantages

Having a lower damper has several advantages. The main advantage is the ability it gives to control the temperature in the room. Because fireplaces are a relatively inefficient means of heating a home, dampers help to combat the inefficiency. In addition, chimneys are designed to create an updraft of air to safely sweep smoke from the fire out of the house, and they continue to pull air whether there is a fire or not. By closing the lower damper, located just above the firebox, the airflow is restricted and warm air stays in the room rather than escaping up the chimney. A closed lower damper also seals off the chimney from the house, preventing rain or debris falling down into the fireplace.

Disadvantages

While the lower damper prevents outside debris from falling into the fireplace, it won't stop debris from entering the chimney. The lower damper creates a seal just above the firebox, but above the damper, the chimney is open to the elements or even small animals, birds or insects. In addition, throat dampers are usually made of metal, and as such, they can be susceptible to warping or rusting over time, which reduces their capacity to prevent air escaping. Also, lower dampers are difficult to install if they're not put in place when the chimney is constructed.

Alternatives

Alternative fireplace dampers include a top-sealing damper, which is mounted at the top of the chimney rather than in the lower section like the throat damper. Top dampers are more easily installed since they fit on the top of the chimney and have the advantage of sealing off the entire length of the chimney from the elements or other unwanted invasions. A second alternative is the balloon damper, which is literally a balloon inserted into the throat of the chimney, and then inflated through a tube. It is strictly for use during the months when the fireplace is not used and must be removed before a fire is lit.