You may dread catching a flu, but your chimney would be at an absolute loss without one. A flue, that is.
Your chimney flue isn’t something you catch – it’s an important component of your fireplace system. A flue is designed to help move smoke and gases safely out of your home while you’re using your fireplace. But what exactly is a chimney flue, and how does it achieve its task?
What Is a Flue?
The best way to think of a flue is as a passageway. It’s built into the chimney, and it allows the exhaust gases created by a fire to exit rather than back up into your living space. Without a functional flue, harmful gases or smoke could accumulate indoors and pose serious health risks.
Usually flues are lined with materials designed to resist heat and corrosion – like clay tiles or durable stainless steel. While these work closely with the flue, they’re considered a distinct chimney component called a flue liner, not part of the flue itself. This lining helps protect the chimney masonry from damage and makes clearing out creosote buildup more manageable, prolonging the life of the chimney by keeping it in good repair.
Are Flues Different From Chimneys?
Yes, flues and chimneys are different – though you’ll always find them together.
- The chimney is the entire structure extending from the fireplace to outside the home or building.
- The flue is one part of the larger chimney system – the interior passageway spanning most of the height of the system.
While chimney and flue are sometimes used interchangeably, they’re not the same thing. As a matter of fact, some chimneys contain more than one flue! One chimney with multiple flues can serve separate fireplaces, wood stoves, or other appliances that require venting.
And where does the chimney liner come into play? The liner is what protects the interior walls of the flue, ensuring smoke, heat, and acidic gases can’t wear away the brickwork or make their way into your home.
How Does My Chimney & Fireplace Work?
To better understand how a fireplace works, it helps to know what the different components do to contribute to combustion and venting combustion gases.
1. The Firebox & Combustion Process
The fireplace, or more specifically the firebox, is where combustion takes place. Every fire needs fuel and oxygen to start and keep going. As the fuel burns, the chemical reaction of combustion takes place – this is when oxygen reacts with fuel to produce heat and light. During this reaction other byproducts are also produced, such as carbon dioxide, water vapor, and particulate matter.
As we learned in elementary school science, heat always rises. The heat generated by combustion creates a natural updraft. This is the force that drives the exhaust gases into the chimney. This updraft also draws oxygen into the fire, since cooler air from the room moves in to replace the rising air. When this process works well, it ensures that smoke is directed up and out of your living space and your fire gets the oxygen it needs to keep burning its fuel.
2. The Chimney Takes It From There
As the hot gases rise, they enter the chimney, which houses the flue. A few components help out here. First, the damper. Moving the damper to an open position allows the movement of air in the chimney. (Be sure to close it when the fire is over, however, so you don’t trade your warmed air for cool air from outdoors.) Meanwhile, the smoke shelf helps prevent downdrafts, and the smoke chamber funnels smoke into the flue.
The design of the chimney and flue ensures that the combustion byproducts are vented outside. For instance:
- Draft: The flue helps maintain a consistent upward flow of air to keep the combustion process going – and, of course, keep gases from building up in your home. The draft is influenced by factors like the height of your chimney, the temperature difference between the outside air and air inside the chimney, and the diameter of the chimney flue.
- Flue Lining: The flue lining helps the flue out by acting as a smooth, heat-resistant pathway for the exhaust gases to travel through. If a flue liner is damaged, ill-fitting, or worn out, the high temperatures of the gases could cause costly damage to the chimney structure or increase the risk of a chimney fire.
- Making the Escape: The flue leads to the top of the chimney, where the gases are released. As with the flue liner, the flue receives a little extra protection here, too. The chimney crown is a masonry slab at the top of the chimney which helps keep the elements at bay. The chimney cap then sits at the very top of the chimney and acts as a barrier against debris, animals, and rain. These help keep the flue (and the rest of the chimney) free of moisture and blockages.
3. Maximizing Efficiency
For your fireplace to work well, each component needs to be in good order. Proper installation is the right start, and with good maintenance, it sets the foundation for years of enjoyment.
If you’re experiencing trouble with your fireplace – poor combustion, smoke entering your room, diminished efficiency, or other issues – let our team step in to get your system back in prime order. There’s no reason to put up with an underperforming fireplace when friendly, experienced service is a phone call away. We’ll work with you to find solutions that make the most of your fireplace.
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Once your flue is operating smoothly, inspections, maintenance, and regular sweeping help keep it that way. Understanding how your fireplace and its components work can give you a new appreciation of what happens behind the walls of the chimney. But when everything is operating well, all that’s really left is to unwind and enjoy all that your fireplace has to offer!
If you need to book maintenance, don’t wait to get in touch. Call or book online with The Chimney Doctor today.
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