Under the brilliant Texas, builders and homeowners alike install fireplaces into our homes. The joke in Houston is that we have eight months of summer, and four months of the weather trying to decide if its summer or not. There may be two days a year were the temperature falls enough for us to use the fireplace.
I know that when I inspect a fireplace here that I can find an item which will cause me to mark it as in need of repair. Generally there will be three main issues to look for: 1) the screen in front of the firebox is missing or damaged; 2) the damper is missing or damaged; and/or 3) creosote build-up. The screen helps keep burning embers from falling/flying out of the chamber into your home. If you are not use to being around a fire, you may wonder about flying embers. Did you ever burn a piece of paper in science class? This test works best with a hundred dollar bill. Take the bill and burn on edge. As it burns, let go, and you will see it float up and over. (I hope you realize that the bit about the bill being of a hundred dollar value was a joke- just being safe). The damper is the device which closes off the chimney from the firebox. It will serve two purposes in Houston. It prevents chimney swallows from coming all the way down into your house. If you have this problem, your chimney cap has a problem. It prevents your conditioned air from escaping up the chimney. The last issue is the creosote build-up. Creosote is a compound created during the burning of a material, like a log, and it can rise into the chimney, where it settles along the sides of your flue. Creosote can re-ignite, like charcoal, causing a fire in your flue.
Those are the three most common issues in Houston. In any area were fireplaces cannot be used often do to outside temperatures, you will find these concerns, since we do not know that we should be taking care of our fireplaces. A common concern around the country would be are combustible materials close to the opening. Look at the opening for your fireplace to estimate its square footage (height x width). If it is less than six square feet, the hearth extension should be sixteen inches deep and eight inches to the sides. Greater than six sq ft, the hearth extension should be twenty inches deep and twelve inches to the sides. The extension should be at least two inches thick. No material that can burn can be within six inches of the opening. For every inch beyond this six inches, you can have a combustible material stick out another 1/8 of an inch till you reach twelve inches, so for seven inches a 1/8 projection, and for eight inches a 1/4 inch projection.
There are other concerns for fireplaces and chimneys, but these items seem to be the most common.