What causes cracks in your chimney and chimney flue? The answer matters -- if you don’t think your chimney will develop cracks, you won’t keep an eye out for them.

And then you won’t have the opportunity to make a quick repair before a small problem grows into a big one. That "big problem" can range from expensive repointing/brick replacement to dangerous gases leaking into your home, threatening the health of you and your family.

Here are five signs you have increased risk for chimney cracks:

1. You live in an area with a rapid freeze-thaw cycle and you use the fireplace intermittently. This especially true for wood-burning fireplaces. The biggest culprit is moisture. What starts out as water vapor becomes tiny droplets of water. These droplets settle into fissures in your chimney – and freeze if when the temperature drops and you’re not using your fireplace.

Then, since it’s gotten cold again, you fire up the fireplace, and melt that water. The next day you decide not to have a fire – and the water freezes into those fissures, spreading them open like a pair of pliers. A couple of winters of this, and you have a real problem.

2. You live in an area that’s just plain cold. Long, cold winters also put heavy wear-and-tear on the chimney. Again, moisture is the problem. Water is called the "universal solvent" for a reason – it’ll dissolve anything given enough time. Look at the Grand Canyon.

When you get lots of moisture in a chimney, the water’s solvent properties go to work on the water, concrete and bricks, slowing removing one particle at a time until you have fissures, and eventually, cracks, especially if you don’t havea flue liner or other flue protection. If you’re getting heavy use out of a chimney, you’ll speed up the deterioration process.

3. You have a high-energy efficiency furnace. Today’s high-efficiency furnaces save you money, but they also put a lot more moisture in the flue air than yesterday’s lower-efficiency ones. All that moisture, again, increases the wear-and-tear on your chimney and flue.

4. You have an oil or gas furnace. In these cases, the problem is acid. Acidic vapors from burning gas and oil build up a residue and that eats away at your chimney from the inside out. This can cause cracks in the clay lining, especially, and leave you with potentially expensive repairs.

5. Your chimney isn’t properly protected. Making sure that your top plate and rain cap remain in good condition, to prevent moisture from running into the chimney. Rodents, tree limbs and severe weather can all damage these.

Another option to prevent moisture and acid buildup from putting such heavy wear-and-tear on your chimney are chimney flue liners. These products range from smooth wall liners that prevent moisture and acid from attaching to interior chimney walls at all to simple protective devices that catch that residue.

The bottom line: No matter what kind of chimney you have, regular inspections can help give you peace of mind. Visually inspect exterior walls, bricks and mortar for signs of cracking. Use your fingers to see if mortar remains firmly in place, or chunks away.

For interior chimney inspections, consider a using an inspection mirror with a telescopic handle. Coupled with a flashlight, the mirror will help you conduct a visual inspection and spot any signs of cracking.