Chimney Dampers 101

Most chimney dampers sit just above a fireplace’s firebox and are opened and closed with a handle or similar device. Less common are top-mount dampers, which are installed at the top of the chimney structure. Dampers perform two critical jobs.

Job 1. Dampers open to allow smoke to draft

Your chimney flue is (or should be) correctly sized to draft smoke from your fireplace. Optimal drafting can happen only when the fireplace damper is fully open. This allows enough air to move into the firebox, keep the fire burning efficiently and send smoke and harmful gases up the chimney.

Job 2. Dampers close to restrict air flow and prevent home-infestation

When your fireplace isn’t in use, a fully closed, tightly sealed damper keeps conditioned air (both warm and cool) inside your home while preventing unconditioned outside air (both cool and warm) from infiltrating.

Closed dampers also keep out whatever types of critters may have gotten into your chimney flue. Squirrels, birds, snakes, rodents, bats and other creatures are known to inhabit chimneys, and many of them are happy to go into the house and make themselves at home.

(NOTE: You can solve the critter problem with a custom full-width chimney cap, which also keeps debris out of your chimney.)

How fireplace dampers become damaged

Several things can affect a damper’s structure, which primarily consists of plates and a clamp mechanism. Years of heat from your fireplace can eventually cause the plates to warp. Chimney leaks that allow incoming water to settle on the damper can cause rusting.

In either case, you likely won’t know about the early stages of damage, because you can’t easily see every part of the damper assembly. This is one of the reasons why annual fireplace and chimney inspections are so important.

Signs that your damper is damaged

Keep an eye/ear out for:

• Squeaks or scrapes heard when opening or closing the damper
• Water or debris in the firebox at times the damper is thought to be closed
• Small animals like those listed above showing up in your home
• Fires that are hard to start and keep burning robustly due to lack of air
• Smoke backing up into your home
• Drafts in your home that have no other logical explanation

The danger of faulty drafting

Probably the biggest concern with a damaged or malfunctioning damper is that smoke could enter your home. Smoke carries with it carbon monoxide, which is invisible and odorless but is known to be potentially fatal to people and pets when inhaled.

Another serious problem is that of excess smoke and creosote buildup. Without sufficient air (oxygen), a wood fire will burn sluggishly and create more smoke than an aggressively burning log stack. Assuming a good portion of this smoke makes it into the chimney, it will add increasing amounts of creosote deposits to the interior parts of the chimney system.

Creosote, as you probably know, is highly flammable and is responsible for most chimney fires each year in the U.S.

A1 Chimney Specialist of Winchester, TN and Huntsville, AL, can help with any fireplace damper issues you may be having. We’ll perform a thorough inspection to find out what’s wrong, then we can either repair the damper or replace it.

Speak with a certified fireplace and chimney technician in Winchester at (931) 967-3595 or in Huntsville at (256) 285-4895.