What does flue look like in chimney?

Author: Sebastian Raynor  |  Last update: Thursday, September 4, 2025

Inside a chimney you'll find one or more vertical passageways called flues. Ideally, each appliance connected to the chimney (such as each fireplace, each furnace, each wood stove) has its own, separate flue. More than one flue might be contained in one masonry chimney.

How do I know if my chimney has a flue?

A chimney contains a flue (some chimneys will contain more than one flue). > Flue - this is the space or cavity within the chimney which allows the smoke and gases from your fire to pass up, away from the fire, and out of your home. As you can see a chimney is the structure which contains the flue.

What does a flue look like on a fireplace?

Fireplace Flue Tiles: The vertical passageway up the inside of the chimney is the flue. The damper is often (mistakenly) called the flue, but the flue is the passageway. Clay flue tiles are the most common material used to line masonry chimneys when built.

How do you know if your chimney flue is open or closed?

Inspect Visually

Carry out a visual inspection of the chimney from your fireplace. If you can see open dampers or see the sky, that will prove that the flue is open. Failure to see the sky implies a closed flue or one that may need unclogging.

Where is the flu in a chimney?

A typical chimney will have one or more flues that go up through the roof. The flues will carry the hot gas and smoke from the fire up through the roof, where it can escape into the air. This process helps to heat up the air in the house and to distribute the smoke away from people and animals.

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How to tell how many flues are in a chimney?

A flue is a venting system. Each system needs its own flue, so if you heat your home with gas and have a fireplace, you would have two flues. Often times they are in one chimney, so if you were to look down the chimney, it would be separated into two venting systems within the one chimney.

What are the symptoms of a flue?

Symptoms
  • fever* or feeling feverish/chills.
  • cough.
  • sore throat.
  • runny or stuffy nose.
  • muscle or body aches.
  • headaches.
  • fatigue (tiredness)
  • some people may have vomiting and diarrhea, though this is more common in children than adults.

How do I know if my chimney flue is blocked?

Some of the warning signs that could be due to a flue obstruction include:
  • Your carbon monoxide (CO) detector is sounding an alarm.
  • The fireplace fills with smoke.
  • Difficulty lighting a fire.
  • Fire burns out quickly.
  • Black, tarry flakes inside the flue.
  • Strange odor inside the firebox.

Is it bad to leave your chimney flue open?

It's best to keep the flue closed when the fireplace is not in use. Should it stay open for too long cold air, debris, rain, and even animals can make their way inside your home.

What should an open flue look like?

Depending on the type of flue you have, you may actually see daylight coming in from the top of the chimney, or an open metal tube that you can see daylight through. If the tube is closed or you can't see daylight, your flue is likely closed—or in need of serious unclogging.

Do all chimneys have a flue?

So, yes, all chimneys have a flue. And no, your fireplace cannot function without a working flue.

How often should you clean your chimney?

The NFPA recommends that all chimneys be cleaned and inspected annually because if the system is compromised, it creates a fire hazard. It's best not to merely assume that a chimney system is in good working condition, no matter the circumstances.

Is a flu and a damper the same thing?

The damper and flue are two different parts, but they are related and involved in the same function. The flue is the inside tunnel of your chimney that brings gases from your fireplace out of your home, while the damper closes or opens the access to the flue.

Do old chimneys have flues?

Clay tile flues are common in older homes and masonry chimneys. These flues have interlocking terra cotta tiles stacked vertically inside the chimney. Clay tiles are durable and can withstand high temperatures, making them suitable for different fuel types.

How do you open your chimney flue?

You can reach inside of the fireplace opening and behind the lintel to touch the damper. You should be able to open and close it with a knob (this is usually located on the front face of the fireplace) or rod (located in the fireplace, above the firebox).

How often should a chimney flue be replaced?

The average lifespan of a chimney flue liner is about 15 to 20 years. If you lived in your home 15 years or more you probably need to get the entire liner replaced to make sure it is up to code. If there is damage to your chimney flue liner your home is at risk for a serious home fire.

Should I close my chimney flue in the summer?

The primary reason to close your fireplace's damper during summer is to protect it from humidity and any extreme weather events that are commonplace during this season. Closing the damper also prevents critters from getting in and setting up their homes, which can cause flue blockage, poor airflow, and foul odors.

How long does a chimney flue last?

Again, their lifespan depends on routine maintenance and usage, but it's common for metal chimney liners to last up to 25 years. Cast-in-place liners are the most robust because they're typically constructed from cement, and with proper care, you can get up to 50 years from a cast-in-place liner.

How to unblock a chimney flue?

Push the blockage down the flue using a wire chimney brush with the same diameter as your flue. You might get lucky and dislodge it with a couple of prods. Other times, you'll need to cajole the clog down to the fireplace, adding extending rods so the chimney brush can reach.

How do you check a chimney flue?

A new flue can be checked by: A) Carrying out a visual inspection to check that the lining, liners or flueblocks are of the correct materials and of suitable size. C) Carry out a smoke test and (if needed) a flue spillage test.

How much does it cost to unblock a chimney?

The cost of chimney sweeping varies based on the specific type of fireplace or stove. Gas fireplaces, which generally accumulate less residue than wood-burning variants, cost on average between £60 to £90 for a sweep. Wood-burning fireplaces, with their traditional design, usually range between £80 to £100.

How do you get rid of a cold flue?

Do
  1. get plenty of rest.
  2. drink lots of fluid, such as water, to avoid dehydration.
  3. eat healthy food (it's common for small children to lose their appetite for a few days)
  4. gargle salt water to soothe a sore throat (not suitable for children)
  5. drink a hot lemon and honey drink to soothe a sore throat.

Can flue be cured?

Just because there is no cure does not mean there is no way to feel better when you have the flu. There are several over-the-counter medicines available to you to help you combat the symptoms you feel while you are sick with the flu. And some medicines treat multiple symptoms in a single product.

What happens when you have a flue?

They usually include fever, chills, headaches and aching muscles, and you can often get a cough and sore throat at the same time. Flu is caused by viruses and not bacteria, so antibiotics won't treat it.

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