Fix Gaps in the Firebox Brick Mortar
Gaps in the brick mortar on the inside of your fireplace develop over time. With the constant expansion and contraction of materials caused by the fireplace's extreme heat, it's natural that bits of mortar on the refractory firebricks will loosen and fall. Fire can seek a path through the gaps and burn the house's structural elements. Fix mortar gaps inside the fireplace's firebox with a mineral-based filler called fireplace mortar or refractory caulk. For this simple fix, you'll only need a putty knife to clean out the loose mortar and a can of compressed air to blow out the rest. After that, it's just a matter of caulking the joints.
Clean the Chimney
Unlike gas-powered and gel fireplaces, wood-burning fireplaces generate an immense amount of heat and smoke. Creosote cakes up on the inside of the fireplace flue and can accelerate a chimney fire—a terrifying event that must be put out by the fire department. Chimney cleaning rids your flue of potentially hazardous creosote and other flammable debris. The chimney is cleaned from top to bottom, including the ashes in the firebox. Buy your own chimney-cleaning tools and do the job yourself or call a local chimney cleaning service or chimney sweep.
Inspect and Repair the Flashing
Metal flashing that runs between the chimney and the roof is your protection against water making its way into your home. Flashing can tear away or fold back from falling limbs or even from pesky birds or squirrels. Inspect your roof flashing to make sure that it is intact. Repair the flashing as needed.
Buy the Right Firewood
Your fireplace is only as good as the wood that you burn in it. Burning the incorrect type of wood quickly dirties the inside of the fireplace and can lead to more frequent cleaning. Though softwoods tend to be less expensive than hardwoods, they burn faster and leave a fine ash that is difficult to clean up. They also create creosote faster.
Fix the Outside of Your Brick Chimney
With an extension ladder and a few simple masonry tools, you can repoint any missing brick mortar, patch cracks in the crown, and repair or replace bricks. With a caulking gun, caulk around the flue and the crown.
Clean the Fireplace Bricks
No matter how well your fireplace draws or how airtight your fireplace screen appears to be, smoke inevitably finds its way out of the firebox. Depending on how heavily blackened the fireplace bricks are, you can clean them with mild, moderate, or strong methods.
Mild: Warm water mixed with dishwashing detergent is an effective grease-cutter. Scrubbing with table salt provides a mild abrasive.
Moderate: Dishwashing detergent, ammonia, and pumice step up the cleaning game. Ammonia is a stronger grease-cutter and pumice is a harsher abrasive.
Strong: Thickly blackened chimney bricks may require cleaning with hot water and tri-sodium phosphate (TSP).
Replace the Fireplace Screen
Prevent burning embers and ashes from leaving the firebox to keep your house clean and safe. If you're having problems with embers or sparks migrating to your living area, it probably means that you need a new fireplace screen. Or you might just want to change out your current screen for a fresh look. Fireplace screens can rest near or even against the fireplace, and they come in a wide range of styles and metals. Prevent smoke from escaping the firebox, by installing a glass fireplace screen. These heat-proof glass inserts hold back most of the smoke while still allowing heat to pass into the home.
Repair, Build, or Spruce up the Mantel
If your fireplace has had its mantel for a long time, it might be showing its age. Or you might just be tired of it. Either way, you can build a new fireplace mantel from live-edge wood or walnut stock. Or you might like your fireplace mantel to look like an old railroad tie—a faux one, of course. If you're not interested in woodworking, consider redecorating your mantel for an entirely new look.
Properly Store Your Firewood
Store your firewood in a rack that you keep outside of the house in a dry area. Be sure to keep vermin and insects away from the firewood since they can get transported into your house.
Hire a Professional to Fix Your Fireplace
Exterior chimney repair can be a big project, so call a chimney repair specialist or mason if you feel that the work is beyond your scope. Minor exterior chimney defects are worsened by the outside elements and quickly turn into major problems. Wet ceilings, damp attic insulation, and mushy wall drywall are some of the interior problems that can result from an improperly maintained chimney and flashing.
https://www.thespruce.com/fireplace-maintenance-tips-5078136