What is a Chimney?

A chimney is a vertical pipeline that is built to move fumes, smoke and other by-products of burnt materials and fire from the bottom of the channel through the roof of the structure. A chimney is a tunnel type of structure above a fireplace, though in other English-speaking countries, sometimes the term chimney is used to refer to a stove hood as well. A chimney is also the pathway Santa Claus has used to enter and leave a home during his Christmas visit. Since the chimney is the structure that rises out of a fireplace, it needs to have parts and structures that can handle the higher temperatures and possible flames associated with a fireplace.

There are two basic types of chimneys. Ones that are pre-built from metal and these types of chimneys can be used with wood-burning appliances. The other type is a masonry chimney that is generally built from clay, brick or stone. In either case, stainless steel inserts are used to account for any damage or imperfections within the chimney.

What is a Chimney Flue?

The flue is the vertical passage or chimney duct that runs from where the fire burns to the roof. The flue is the interior portion of the channel that leads to the roof and then outside. The flue can be a clay, brick, or metal channel installed inside of a chimney, intended to contain the products produced from combustion and to direct them to the outside. The flue is also there to protect the interior of the chimney lining. Flues can have liners to protect them from all that travels through them.

What is the Difference Between Flue and Chimney Ducting?

The flue is the passageway that allows smoke, gas, or products of combustion to escape outdoors. Flexible chimney ducting, vent pipes, and masonry channels that lead to the roof are just verities of flues.

What is Ducting in a Chimney?
A duct in a chimney is where a large pipe is used to expel the smoke and heat from the firebox. The chimney duct directs the hot air and other contaminants from the burn area (i.e., firebox) to the outside of the house making it more habitable.

Transferring hot air and by-products of burnt wood or other materials is a critical matter. The proper type of material needs to be used so that the duct does not deteriorate, burn or be affected by predictably hot and incendiary materials. The use of improper chimney ducts and duct materials can lead to complications.

What is a Damper in a Chimney?
Sometimes the damper and flue are accidentally mixed up. The damper and flue are two different features in a chimney. The flue is the inside tunnel of your chimney, while the damper is the structure that closes or opens the entrance to the flue.

“Aluminum Flex 280 – Compressible”

“Aluminum Flex 280 – Compressible”

What Are Common Chimney Flue Dangers?

1. The flue and its liner can deteriorate or get damaged. Flue liners regardless of the material makeup (for example if they are stainless steel, or other materials) can be damaged and allow the elevated temperatures to degrade the chimneys’ structure.
2. Creosote buildup can cause fires. Creosote is deposited in the chimney lining when the fireplace burns. Creosote is a kind of soot that can form in a chimney as wood burning materials are used to heat the home. Wood never burns consistently and burning wood sometimes causes an incomplete burn of the oils in the firewood. As the smoke from a wood burning fire travels up the chimney, it contains wood particles, gases, and a variety of other components. As the materials travel up, they cool and condense along the chimney walls. It is this condensation that turns into creosote. Creosote is extremely combustible and should be attended to and removed.
3. A flue that is blocked or obstructed can be dangerous. Flue obstructions can include debris that travels from the roof down, or animal nests, and these can send gas vapors (e.g., Carbon monoxide) and smoke back down into the home.

“Bridge Clamps”

“Screw Clamps”

How Hot Can a Chimney Pipe Get?

Combustion of wood has several stages and understanding how wood burns help the chimney or stove operator burn timber in a safer way. Different lumber materials burn in different ways. The density of the wood, the unique components of each piece of timber, the amount of moisture left in the wood and other details work to affect the temperature at which a piece of firewood burns. If we break down the burning of wood in a fireplace to three stages, the first stage is when the wood is heated to evaporate the moisture left in the wood. Wood burns at about 500 Fahrenheit and volatile matter is vaporized. At about 1,100° Fahrenheit these volatile vapors scorch. Once the volatile vapors have burned, the remaining solids are charcoal, and this burns temperatures topping 1,100° Fahrenheit. The amount of fuel you use (i.e., firewood), the type of wood, the addition of lighter fluid that can fuel the fire (though not recommended), all can affect the temperature levels your chimney’s flue will experience. Since temperatures in a chimney get as hot as noted, the operator needs to use materials that can handle this type of exposure. The chimney ducts used must be able to handle the maximum of these extreme temperatures. Stainless-steel chimney ducts are a great choice since there is a version of these that can handle up to 1650 Fahrenheit. Also, it should be noted that chimneys have a high possibility of fire extending beyond the fire box. Fire is a constant danger in and around chimneys. According to FEMA, from 2017 to 2019, an estimated average of 34,000 heating fires in residential buildings were reported to U.S. fire departments each year.

“SSti-Flex 1650”

“SS-Flex 800”

Using Stainless-Steel Chimney Ducts

Transferring hot air and chemicals through a fireplace flue is heavy-duty work. The improper chimney duct installation can lead to complications such as fire hazards, structural damage to the chimney, and hazardous materials and fumes coming back into the building. To handle the high temperature operating conditions, it is recommended that you use heat resistant stainless-steel chimney ducting. By using stainless steel chimney ducts to move heat and smoke in a chimney, you can protect your brick or clay chimney from corrosion and damage.

Corrosion is a serious issue that significantly reduces the lifespan of a fireplace flue. Fortunately, stainless steel and aluminum resist corrosion damage caused by moisture, chemicals, and fumes. Our stainless-steel chimney ducts are an excellent long-term investment because they are resistant to chemicals and materials that would cause severe damage to clay and brick chimney ducts. Along with great resistance to corrosive materials, the stainless-steel construction of some of our hose materials is heat resistant up to 1,650 degrees Fahrenheit.

With temperature resistance up 800 and 1,650 degrees Fahrenheit (based on the type of hose chosen), our stainless steel chimney ducts are perfect for the high temperature demands of chimney ventilation. Using a heat resistant fireplace flue is extremely important for the safety of fireplace operations as well as the integrity of the chimney structure itself. Using a flexible chimney duct that is made of stainless steel or aluminum protects you from the risk of costly structural damage to your chimney. An added benefit to our heat resistant flexible chimney liner is the metals’ excellent durability.

“SS-Flex 800”

Aluminum – A Less Expensive Chimney Duct Option

Aluminum is another metal that does not burn. Aluminum is a distinctively fireproof chimney exhaust duct material. Aluminum flex ducts have a natural oxide layer that prevents the metal reacting with oxygen and causing detonation. Aluminum ducts do not burn. But at a temperature of 400°F they will start to fail and at 1100-1200°F these hoses will melt, but they will not combust. Aluminum when used as a chimney exhaust duct, should be done further down the line where the temperature of the flue is below 400°F.

Looking at the product itself, it is easy to see why aluminum chimney ducts are a good flexible chimney liner choice of many. Aluminum flex ducts come in sections of 5 and 10 feet long – a few lengths should be more than sufficient to provide ventilation for all by the tallest of chimneys. Additionally, if you choose to connect the aluminum ducting, hose connectors are a commonplace accessory that can be found in multiple different sizes.

Aluminum ducting is available in interior diameters (I.D.) the run from as narrow as two inches across to 12 inches in diameter.

Just like the stainless chimney exhaust ducts, aluminum ducts are flexible and feature self-supporting construction. This durable feature gives you the flexibility to bend and maneuver the hose to provide great airflow for your chimney, while at same time giving the chimney great stability and durability. These flexible chimney ducting products are also crush resistant, allowing them to be resistant to damage from external sources.

We know protecting your chimney is a concern and is why you are browsing this page. Thankfully, by using chimney hoses, you will be alleviating one of the biggest damage risk factors to a flue. Though the capability for damage may seem overstated, it is more of a risk than it may seem. In 2013, for example, chimneys and fireplaces were responsible for roughly 23,000 residential fires in the United States (according to information obtained from the United States Fire Administration). Protective duct for chimney lining is available in stainless-steel or aluminum which are both metals that do not burn. Take a look at our online catalog of products to find the perfect flexible chimney hose product. If you would like assistance on selecting the perfect product for you, give one of our ducting specialists a call today at 1-800-370-9152.

“Aluminum Flex 400”