Flies are annoying pests that can enter you home during the spring, summer and fall months. They may enter through an open door or window or use your fireplace as an entry point. Ridding your home of flies that enter through the fireplace can prove challenging. Before you can remedy the fly issue, you must determine the underlying cause of the problem.
Remove any animals trapped in the fireplace. Flies in the fireplace are often caused by a dead animal, such as a rat, bird or squirrel, that is trapped there. Get rid of the trapped animal to alleviate the underlying cause of flies. Purchase a chimney sweep from your local hardware store -- a long pole with an attached brush designed to clean and clear any debris in the fireplace. Climb on top of your roof, and stick the sweep down your chimney flue, which is the vent that allows smoke and gases to escape the chimney. Move the chimney sweep around to dislodge and remove the trapped animal.
Burn a fire to kill flies. Removal of any animal in the fireplace will prevent new flies from entering the chimney, but it won't kill the existing flies. If you have a wood-burning fireplace, start a fire to kill any remaining flies.
Position an insect bomb in your fireplace. If you have a gas fireplace or don't want to start a fire, purchase an insect bomb from the grocery store. These insecticides release a fume in the air that kills insects. Choose one that works on flies, and read the instructions before using. You will need to leave the house for a few hours once you set the bomb.