Eliminating unpleasant odors from your AC vents can feel like a never-ending battle. You spray air fresheners, change your filters, and yet that funky smell persists. The key to winning this war on stink isnt masking the odor, its identifying and addressing the root cause. And the first step in that process is pinpointing the source of the smell.
Think of your AC system as a giant lung, breathing in and exhaling air throughout your home. Anything getting sucked into that system has the potential to create odors. Dust, pet dander, and even dead insects can accumulate on the filter and evaporator coil, creating a breeding ground for mold and mildew. These microbial growth are often the culprits behind that musty, mildewy smell.
Another common source is stagnant water. AC units naturally produce condensation, which is typically drained away. However, a clogged drain line can lead to standing water, creating a perfect environment for bacteria and algae, resulting in a sour or swampy odor.
Beyond the system itself, consider the surrounding environment. Is there something near the intake vent, like a garbage can or pet bedding, thats contributing to the smell? Even something seemingly innocuous like a damp carpet or nearby construction can introduce odors into the system.
Sometimes, the smell isnt biological at all. A burning smell could indicate an electrical problem, requiring immediate professional attention. A sweet, chemical odor might be a refrigerant leak, which is not only unpleasant but also potentially harmful.
Identifying the source requires a bit of detective work. Start by checking the air filter. Is it dirty or damp? Then, inspect the area around the vents, both inside and outside the house. Look for signs of moisture, mold, or any unusual debris. If the smell is particularly strong or unusual, its always best to consult a qualified HVAC technician. They have the tools and expertise to diagnose the problem accurately and recommend the appropriate solution. By taking the time to identify the source, you can effectively eliminate the odor and breathe easy knowing your homes air is fresh and clean.
Eliminating unpleasant odors is a common household chore, and while masking them with air fresheners might offer a temporary fix, truly getting rid of the source of the smell requires effective cleaning methods. Its not just about making your home smell nice; its about creating a healthier and more pleasant living environment. Heres a look at some proven strategies for tackling those pesky odors.
One of the most fundamental steps is identifying the source. Is it the garbage disposal, a lingering pet accident, musty towels, or something else entirely? Once youve pinpointed the culprit, you can choose the right cleaning method. For example, a baking soda and vinegar paste works wonders on absorbing odors in carpets and upholstery. Sprinkle baking soda on the affected area, let it sit for a while, and then vacuum it up. For tougher stains, mix the baking soda with a little water and vinegar to form a paste, apply it to the stain, let it dry, and then vacuum.
Kitchen odors are often related to food debris. Regularly cleaning the refrigerator, wiping down countertops, and emptying the garbage can prevent unpleasant smells from taking hold. The garbage disposal can be freshened with citrus peels or ice cubes and a bit of dish soap. For lingering odors in microwaves, try heating a bowl of water with lemon slices for a few minutes. The steam will help loosen any stuck-on food particles and neutralize odors.
Bathrooms are another common source of unpleasant smells. Ensure proper ventilation by running the exhaust fan during and after showers to prevent mildew growth, a common cause of mustiness. Regularly cleaning the toilet, shower, and sink with disinfecting cleaners can also help keep odors at bay. Dont forget to wash bath mats and towels frequently.
Pet odors can be particularly challenging. Enzyme-based cleaners are specifically designed to break down pet urine and other organic matter, effectively eliminating the source of the smell. Regularly washing pet bedding and vacuuming areas where pets spend a lot of time can also make a big difference.
Finally, remember that good ventilation is key to preventing and eliminating odors. Open windows whenever possible to allow fresh air to circulate. Using an air purifier with an activated carbon filter can also help remove airborne odors and improve indoor air quality. By combining these effective cleaning methods and focusing on the source of the odor, you can create a fresher, cleaner, and more pleasant home environment for everyone.
Nobody likes that musty, stale smell that sometimes wafts from the AC vents. Its not just unpleasant; it can be a sign of mold, mildew, or other unwelcome guests lurking in your ductwork. Thankfully, preventing future odor buildup is often easier than dealing with the problem after it arises. A few simple habits can make a big difference.
First, regular filter changes are crucial. Think of your air filter as the lungs of your HVAC system. A dirty filter restricts airflow, traps dust and debris, and creates a breeding ground for odor-causing microbes. Aim to change your filter every 1-3 months, or even more frequently if you have pets or allergies.
Next, consider your AC units drain pan. This pan collects condensation, and if it doesnt drain properly, stagnant water can become a source of nasty smells. Make sure the drain line is clear and flowing freely. You can pour a mixture of vinegar and water down the drain line periodically to help prevent clogs and kill any lingering bacteria.
Another smart move is to schedule regular HVAC maintenance. A professional technician can inspect your system for any underlying issues, clean the coils and other components, and ensure everything is running efficiently. This can not only prevent odors but also improve your systems performance and lifespan.
Beyond professional maintenance, there are some DIY steps you can take. Running your fan in "on" mode, rather than "auto," can help circulate air and prevent moisture buildup. You can also use commercially available vent and duct cleaning products, but be sure to follow the instructions carefully and choose products that are safe for your system.
Finally, think about the overall cleanliness of your home. Regular dusting, vacuuming, and controlling humidity levels can all contribute to fresher indoor air. By addressing these factors, you can create a healthier and more pleasant environment while preventing those dreaded AC vent odors from ever taking hold.
That funky smell wafting from your vents? Its not something to just shrug off. While sometimes a simple filter change can do the trick, a persistent or worsening odor is a sign you might need professional AC vent cleaning. Think of your ductwork as the lungs of your home. Over time, dust, pet dander, pollen, mold, and even mildew can build up in there. This creates a breeding ground for bacteria and other microorganisms, leading to those musty, stale, or even downright nasty smells.
If the odor sticks around even after youve swapped out the filter, it’s a red flag. A dirty filter masks the underlying problem, but once its clean, those trapped smells can escape. Similarly, if you notice the smell is stronger after running the AC, it means the system is actively circulating those contaminants throughout your house. This isnt just unpleasant; it can also impact your indoor air quality and potentially exacerbate allergies or respiratory issues.
Another sign you need professional help is if you see visible mold growth around your vents or notice excessive dust accumulation. Dont try to tackle this yourself; disturbing mold can release spores into the air, worsening the problem. Professionals have the right equipment and expertise to safely remove mold and thoroughly clean your ducts, eliminating the source of the odor.
Finally, if youve recently experienced water damage or a pest infestation, its crucial to have your vents inspected and cleaned. These situations create ideal conditions for mold and bacteria growth within your ductwork. Ignoring the problem can lead to significant health risks and costly repairs down the road.
So, while a little DIY air freshener might temporarily mask the smell, addressing the root cause is key. If you’re dealing with persistent or worsening odors from your vents, calling a professional for AC vent cleaning is the best way to ensure a healthy and fresh-smelling home.
The word duct is derived from the Latin word for led/leading. It may refer to:
A clothes dryer (tumble dryer, drying machine, or simply dryer) is a powered household appliance that is used to remove moisture from a load of clothing, bedding and other textiles, usually after they are washed in the washing machine.
Many dryers consist of a rotating drum called a "tumbler" through which heated air is circulated to evaporate moisture while the tumbler is rotated to maintain air space between the articles. Using such a machine may cause clothes to shrink or become less soft (due to loss of short soft fibers). A simpler non-rotating machine called a "drying cabinet" may be used for delicate fabrics and other items not suitable for a tumble dryer. Other machines include steam to de-shrink clothes and avoid ironing.[1]
Tumble dryers continuously draw in the ambient air around them and heat it before passing it through the tumbler. The resulting hot, humid air is usually vented outside to make room for more air to continue the drying process.
Tumble dryers are sometimes integrated with a washing machine, in the form of washer-dryer combos, which are essentially a front loading washing machine with an integrated dryer or (in the US) a laundry center, which stacks the dryer on top of the washer and integrates the controls for both machines into a single control panel. Often the washer and dryer functions will have a different capacity, with the dryer usually having a lower capacity than the washer. Tumble dryers can also be top loading, in which the drum is loaded from the top of the machine and the drum's end supports are in the left and right sides, instead of the more conventional front and rear. They can be as thin as 40 centimetres (16 in) in width, and may include detachable stationary racks for drying items like plush toys and footwear.[2]
These centrifuge machines simply spin their drums much faster than a typical washer could, in order to extract additional water from the load. They may remove more water in two minutes than a heated tumble dryer can in twenty, thus saving significant amounts of time and energy. Although spinning alone will not completely dry clothing, this additional step saves a worthwhile amount of time and energy for large laundry operations such as those of hospitals.
Just as in a tumble dryer, condenser or condensation dryers pass heated air through the load. However, instead of exhausting this air, the dryer uses a heat exchanger to cool the air and condense the water vapor into either a drain pipe or a collection tank. The drier air is run through the loop again. The heat exchanger typically uses ambient air as its coolant, therefore the heat produced by the dryer will go into the immediate surroundings instead of the outside, increasing the room temperature. In some designs, cold water is used in the heat exchanger, eliminating this heating, but requiring increased water usage.
In terms of energy use, condenser dryers typically require around 2 kilowatt hours (kW⋅h) of energy per average load.[3]
Because the heat exchange process simply cools the internal air using ambient air (or cold water in some cases), it will not dry the air in the internal loop to as low a level of humidity as typical fresh, ambient air. As a consequence of the increased humidity of the air used to dry the load, this type of dryer requires somewhat more time than a tumble dryer. Condenser dryers are a particularly attractive option where long, intricate ducting would be required to vent the dryer.
A closed-cycle heat pump clothes dryer uses a heat pump to dehumidify the processing air. Such dryers typically use under half the energy per load of a condenser dryer.
Whereas condensation dryers use a passive heat exchanger cooled by ambient air, these dryers use a heat pump. The hot, humid air from the tumbler is passed through a heat pump where the cold side condenses the water vapor into either a drain pipe or a collection tank and the hot side reheats the air afterward for re-use. In this way not only does the dryer avoid the need for ducting, but it also conserves much of its heat within the dryer instead of exhausting it into the surroundings. Heat pump dryers can, therefore, use up to 50% less energy required by either condensation or conventional electric dryers. Heat pump dryers use about 1 kW⋅h of energy to dry an average load instead of 2 kW⋅h for a condenser dryer, or from 3 to 9 kW⋅h, for a conventional electric dryer.[4][5][3] Domestic heat pump dryers are designed to work in typical ambient temperatures from 5 to 30 °C (41 to 86 °F). Below 5 °C (41 °F), drying times significantly increase.
As with condensation dryers, the heat exchanger will not dry the internal air to as low a level of humidity as the typical ambient air. With respect to ambient air, the higher humidity of the air used to dry the clothes has the effect of increasing drying times; however, because heat pump dryers conserve much of the heat of the air they use, the already-hot air can be cycled more quickly, possibly leading to shorter drying times than tumble dryers, depending on the model.
A new type of dryer in development, these machines are a more advanced version of heat pump dryers. Instead of using hot air to dry the clothing, mechanical steam compression dryers use water recovered from the clothing in the form of steam. First, the tumbler and its contents are heated to 100 °C (212 °F). The wet steam that results purges the system of air and is the only remaining atmosphere in the tumbler.
As wet steam exits the tumbler, it is mechanically compressed (hence the name) to extract water vapor and transfer the heat of vaporization to the remaining gaseous steam. This pressurized, gaseous steam is then allowed to expand, and is superheated before being injected back into the tumbler where its heat causes more water to vaporize from the clothing, creating more wet steam and restarting the cycle.
Like heat pump dryers, mechanical steam compression dryers recycle much of the heat used to dry the clothes, and they operate in a very similar range of efficiency as heat pump dryers. Both types can be over twice as efficient as conventional tumble dryers. The considerably higher temperatures used in mechanical steam compression dryers result in drying times on the order of half as long as those of heat pump dryers.[6]
Marketed by some manufacturers as a "static clothes drying technique", convectant dryers simply consist of a heating unit at the bottom, a vertical chamber, and a vent at top. The unit heats air at the bottom, reducing its relative humidity, and the natural tendency of hot air to rise brings this low-humidity air into contact with the clothes. This design is slower than conventional tumble dryers, but relatively energy-efficient if well-implemented. It works particularly well in cold and humid environments, where it dries clothes substantially faster than line-drying. In hot and dry weather, the performance delta over line-drying is negligible.
Given that this is a relatively simple and cheap technique to materialize, most consumer products showcase the added benefit of portability and/or modularity. Newer designs implement a fan heater at the bottom to pump hot air into the vertical drying rack chamber. Temperatures in excess of 60 °C (140 °F) can be reached inside these "hot air balloons," yet lint, static cling, and shrinkage are minimal. Upfront cost is significantly lower than tumble, condenser and heat pump designs.
If used in combination with washing machines featuring fast spin cycles (800+ rpm) or spin dryers, the cost-effectiveness of this technique has the potential to render tumble dryer-like designs obsolete in single-person and small family households. One disadvantage is that the moisture from the clothes is released into the immediate surroundings. Proper ventilation or a complementary dehumidifier is recommended for indoor use. It also cannot compete with the tumble dryer's capacity to dry multiple loads of wet clothing in a single day.
The solar dryer is a box-shaped stationary construction which encloses a second compartment where the clothes are held. It uses the sun's heat without direct sunlight reaching the clothes. Alternatively, a solar heating box may be used to heat air that is driven through a conventional tumbler dryer.
Japanese manufacturers[7] have developed highly efficient clothes dryers that use microwave radiation to dry the clothes (though a vast majority of Japanese air dry their laundry). Most of the drying is done using microwaves to evaporate the water, but the final drying is done by convection heating, to avoid problems of arcing with metal pieces in the laundry.[8][9] There are a number of advantages: shorter drying times (25% less),[10] energy savings (17–25% less), and lower drying temperatures. Some analysts think that the arcing and fabric damage is a factor preventing microwave dryers from being developed for the US market.[11][12]
Ultrasonic dryers use high-frequency signals to drive piezoelectric actuators in order to mechanically shake the clothes, releasing water in the form of a mist which is then removed from the drum. They have the potential to significantly cut energy consumption while needing only one-third of the time needed by a conventional electric dryer for a given load.[13] They also do not have the same issues related with lint in most other types of dryers.[14]
Some manufacturers, like LG Electronics and Whirlpool, have introduced hybrid dryers, that offer the user the option of using either a heat pump or a traditional electric heating element for drying the user's clothes. Hybrid dryers can also use a heat pump and a heating element at the same time to dry clothes faster.
Clothes dryers can cause static cling through the triboelectric effect. This can be a minor nuisance and is often a symptom of over-drying textiles to below their equilibrium moisture level, particularly when using synthetic materials. Fabric conditioning products such as dryer sheets are marketed to dissipate this static charge, depositing surfactants onto the fabric load by mechanical abrasion during tumbling.[15] Modern dryers often have improved temperature and humidity sensors and electronic controls which aim to stop the drying cycle once textiles are sufficiently dry, avoiding over-drying and the static charge and energy wastage this causes.
Drying at a minimum of 60 °C (140 °F) heat for thirty minutes kills many parasites including house dust mites,[16] bed bugs,[17] and scabies mites[18] and their eggs; a bit more than ten minutes kills ticks.[19] Simply washing drowns dust mites, and exposure to direct sunlight for three hours kills their eggs.[16]
Moisture and lint are byproducts of the tumble drying process and are pulled from the drum by a fan motor and then pushed through the remaining exhaust conduit to the exterior termination fitting. Typical exhaust conduit comprises flex transition hose found immediately behind the dryer, the 4-inch (100 mm) rigid galvanized pipe and elbow fittings found within the wall framing, and the vent duct hood found outside the house.
A clean, unobstructed dryer vent improves both the efficiency and safety of the dryer. As the dryer duct pipe becomes partially obstructed and filled with lint, drying time markedly increases and causes the dryer to waste energy. A blocked vent increases the internal temperature and may result in a fire. Clothes dryers are one of the more costly home appliances to operate.[20]
Several factors can contribute to or accelerate rapid lint build-up. These include long or restrictive ducts, bird or rodent nests in the termination, crushed or kinked flex transition hose, terminations with screen-like features, and condensation within the duct due to un-insulated ducts traveling through cold spaces such as a crawl space or attic. If plastic flaps are at the outside end of the duct, one may be able to flex, bend, and temporarily remove the plastic flaps, clean the inside surface of the flaps, clean the last foot or so of the duct, and reattach the plastic flaps. The plastic flaps keep insects, birds, and snakes[21] out of the dryer vent pipe. During cold weather, the warm wet air condenses on the plastic flaps, and minor trace amounts of lint sticks to the wet inside part of the plastic flaps at the outside of the building.[22][23]
Ventless dryers include multi-stage lint filtration systems and some even include automatic evaporator and condenser cleaning functions that can run even while the dryer is running. The evaporator and condenser are usually cleaned with running water. These systems are necessary, in order to prevent lint from building up inside the dryer and evaporator and condenser coils.
Aftermarket add-on lint and moisture traps can be attached to the dryer duct pipe, on machines originally manufactured as outside-venting, to facilitate installation where an outside vent is not available. Increased humidity at the location of installation is a drawback to this method.[24]
Dryers expose flammable materials to heat. Underwriters Laboratories[25] recommends cleaning the lint filter after every cycle for safety and energy efficiency, provision of adequate ventilation, and cleaning of the duct at regular intervals.[26] UL also recommends that dryers not be used for glass fiber, rubber, foam or plastic items, or any item that has had a flammable substance spilled on it.
In the United States, an estimate from the US Fire Administration[27] in a 2012 report estimated that from 2008 to 2010, fire departments responded to an estimated 2,900 clothes dryer fires in residential buildings each year across the nation. These fires resulted in an annual average loss of 5 deaths, 100 injuries, and $35 million in property loss. The Fire Administration attributes "Failure to clean" (34%) as the leading factor contributing to clothes dryer fires in residential buildings, and observed that new home construction trends place clothes dryers and washing machines in more hazardous locations away from outside walls, such as in bedrooms, second-floor hallways, bathrooms, and kitchens.
To address the problem of clothes dryer fires, a fire suppression system can be used with sensors to detect the change in temperature when a blaze starts in a dryer drum. These sensors then activate a water vapor mechanism to put out the fire.[28]
The environmental impact of clothes dryers is especially severe in the US and Canada, where over 80% of all homes have a clothes dryer. According to the US Environmental Protection Agency, if all residential clothes dryers sold in the US were energy efficient, "the utility cost savings would grow to more than $1.5 billion each year and more than 10 billion kilograms (22 billion pounds) of annual greenhouse gas emissions would be prevented”.[29]
Clothes dryers are second only to refrigerators and freezers as the largest residential electrical energy consumers in America.[30]
In the European Union, the EU energy labeling system is applied to dryers; dryers are classified with a label from A+++ (best) to G (worst) according to the amount of energy used per kilogram of clothes (kW⋅h/kg). Sensor dryers can automatically sense that clothes are dry and switch off. This means over-drying is not as frequent. Most of the European market sells sensor dryers now, and they are normally available in condenser and vented dryers.
A hand-cranked clothes dryer was created in 1800 by M. Pochon from France.[31] Henry W. Altorfer invented and patented an electric clothes dryer in 1937.[32] J. Ross Moore, an inventor from North Dakota, developed designs for automatic clothes dryers and published his design for an electrically operated dryer in 1938.[33] Industrial designer Brooks Stevens developed an electric dryer with a glass window in the early 1940s.[34]
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A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney effect. The space inside a chimney is called the flue. Chimneys are adjacent to large industrial refineries, fossil fuel combustion facilities or part of buildings, steam locomotives and ships.
In the United States, the term smokestack industry refers to the environmental impacts of burning fossil fuels by industrial society, including the electric industry during its earliest history. The term smokestack (colloquially, stack) is also used when referring to locomotive chimneys or ship chimneys, and the term funnel can also be used.[1][2]
The height of a chimney influences its ability to transfer flue gases to the external environment via stack effect. Additionally, the dispersion of pollutants at higher altitudes can reduce their impact on the immediate surroundings. The dispersion of pollutants over a greater area can reduce their concentrations and facilitate compliance with regulatory limits.
Industrial chimney use dates to the Romans, who drew smoke from their bakeries with tubes embedded in the walls. However, domestic chimneys first appeared in large dwellings in northern Europe in the 12th century. The earliest surviving example of an English chimney is at the keep of Conisbrough Castle in Yorkshire, which dates from 1185 AD,[3] but they did not become common in houses until the 16th and 17th centuries.[4] Smoke hoods were an early method of collecting the smoke into a chimney. These were typically much wider than modern chimneys and started relatively high above the fire, meaning more heat could escape into the room. Because the air going up the shaft was cooler, these could be made of less fireproof materials. Another step in the development of chimneys was the use of built-in ovens which allowed the household to bake at home. Industrial chimneys became common in the late 18th century.
Chimneys in ordinary dwellings were first built of wood and plaster or mud. Since then chimneys have traditionally been built of brick or stone, both in small and large buildings. Early chimneys were of simple brick construction. Later chimneys were constructed by placing the bricks around tile liners. To control downdrafts, venting caps (often called chimney pots) with a variety of designs are sometimes placed on the top of chimneys.
In the 18th and 19th centuries, the methods used to extract lead from its ore produced large amounts of toxic fumes. In the north of England, long near-horizontal chimneys were built, often more than 3 km (2 mi) long, which typically terminated in a short vertical chimney in a remote location where the fumes would cause less harm. Lead and silver deposits formed on the inside of these long chimneys, and periodically workers would be sent along the chimneys to scrape off these valuable deposits.[5]
As a result of the limited ability to handle transverse loads with brick, chimneys in houses were often built in a "stack", with a fireplace on each floor of the house sharing a single chimney, often with such a stack at the front and back of the house. Today's central heating systems have made chimney placement less critical, and the use of non-structural gas vent pipe allows a flue gas conduit to be installed around obstructions and through walls.
Most modern high-efficiency heating appliances do not require a chimney. Such appliances are generally installed near an external wall, and a noncombustible wall thimble[clarification needed] allows a vent pipe to run directly through the external wall.
On a pitched roof where a chimney penetrates a roof, flashing is used to seal up the joints. The down-slope piece is called an apron, the sides receive step flashing and a cricket is used to divert water around the upper side of the chimney underneath the flashing.[6]
Industrial chimneys are commonly referred to as flue-gas stacks and are generally external structures, as opposed to those built into the wall of a building. They are generally located adjacent to a steam-generating boiler or industrial furnace and the gases are carried to them with ductwork. Today the use of reinforced concrete has almost entirely replaced brick as a structural element in the construction of industrial chimneys. Refractory bricks are often used as a lining, particularly if the type of fuel being burned generates flue gases containing acids. Modern industrial chimneys sometimes consist of a concrete windshield with a number of flues on the inside.
The 300 m (980 ft) high steam plant chimney at the Secunda CTL's synthetic fuel plant in Secunda, South Africa consists of a 26 m (85 ft) diameter windshield with four 4.6 metre diameter concrete flues which are lined with refractory bricks built on rings of corbels spaced at 10 metre intervals. The reinforced concrete can be cast by conventional formwork or sliding formwork. The height is to ensure the pollutants are dispersed over a wider area to meet legal or other safety requirements.
A flue liner is a secondary barrier in a chimney that protects the masonry from the acidic products of combustion, helps prevent flue gas from entering the house, and reduces the size of an oversized flue. Since the 1950s, building codes in many locations require newly built chimneys to have a flue liner. Chimneys built without a liner can usually have a liner added, but the type of liner needs to match the type of appliance it services. Flue liners may be clay or concrete tile, metal, or poured in place concrete.
Clay tile flue liners are very common in the United States, although it is the only liner that does not meet Underwriters Laboratories 1777 approval and frequently they have problems such as cracked tiles and improper installation.[7] Clay tiles are usually about 2 feet (0.61 m) long, available in various sizes and shapes, and are installed in new construction as the chimney is built. A refractory cement is used between each tile.
Metal liners may be stainless steel, aluminum, or galvanized iron and may be flexible or rigid pipes. Stainless steel is made in several types and thicknesses. Type 304 is used with firewood, wood pellet fuel, and non-condensing oil appliances, types 316 and 321 with coal, and type AL 29-4C is used with high efficiency condensing gas appliances. Stainless steel liners must have a cap and be insulated if they service solid fuel appliances, but following the manufacturer's instructions carefully.[7] Aluminum and galvanized steel chimneys are known as class A and class B chimneys. Class A are either an insulated, double wall stainless steel pipe or triple wall, air-insulated pipe often known by its genericized trade name Metalbestos. Class B are uninsulated double wall pipes often called B-vent, and are only used to vent non-condensing gas appliances. These may have an aluminum inside layer and galvanized steel outside layer.
Concrete flue liners are like clay liners but are made of a refractory cement and are more durable than the clay liners.
Poured in place concrete liners are made by pouring special concrete into the existing chimney with a form. These liners are highly durable, work with any heating appliance, and can reinforce a weak chimney, but they are irreversible.
A chimney pot is placed on top of the chimney to expand the length of the chimney inexpensively, and to improve the chimney's draft. A chimney with more than one pot on it indicates that multiple fireplaces on different floors share the chimney.
A cowl is placed on top of the chimney to prevent birds and other animals from nesting in the chimney. They often feature a rain guard to prevent rain or snow from going down the chimney. A metal wire mesh is often used as a spark arrestor to minimize burning debris from rising out of the chimney and making it onto the roof. Although the masonry inside the chimney can absorb a large amount of moisture which later evaporates, rainwater can collect at the base of the chimney. Sometimes weep holes are placed at the bottom of the chimney to drain out collected water.
A chimney cowl or wind directional cap is a helmet-shaped chimney cap that rotates to align with the wind and prevent a downdraft of smoke and wind down the chimney.
An H-style cap is a chimney top constructed from chimney pipes shaped like the letter H. It is an age-old method of regulating draft in situations where prevailing winds or turbulences cause downdraft and back-puffing. Although the H cap has a distinct advantage over most other downdraft caps, it fell out of favor because of its bulky design. It is found mostly in marine use but has been regaining popularity due to its energy-saving functionality. The H-cap stabilizes the draft rather than increasing it. Other downdraft caps are based on the Venturi effect, solving downdraft problems by increasing the updraft constantly resulting in much higher fuel consumption.
A chimney damper is a metal plate that can be positioned to close off the chimney when not in use and prevent outside air from entering the interior space, and can be opened to permit hot gases to exhaust when a fire is burning. A top damper or cap damper is a metal spring door placed at the top of the chimney with a long metal chain that allows one to open and close the damper from the fireplace. A throat damper is a metal plate at the base of the chimney, just above the firebox, that can be opened and closed by a lever, gear, or chain to seal off the fireplace from the chimney. The advantage of a top damper is the tight weatherproof seal that it provides when closed, which prevents cold outside air from flowing down the chimney and into the living space—a feature that can rarely be matched by the metal-on-metal seal afforded by a throat damper. Additionally, because the throat damper is subjected to intense heat from the fire directly below, it is common for the metal to become warped over time, thus further degrading the ability of the throat damper to seal. However, the advantage of a throat damper is that it seals off the living space from the air mass in the chimney, which, especially for chimneys positioned on an outside of wall of the home, is generally very cold. It is possible in practice to use both a top damper and a throat damper to obtain the benefits of both. The two top damper designs currently on the market are the Lyemance (pivoting door) and the Lock Top (translating door).
In the late Middle Ages in Western Europe the design of stepped gables arose to allow maintenance access to the chimney top, especially for tall structures such as castles and great manor houses.
When coal, oil, natural gas, wood, or any other fuel is combusted in a stove, oven, fireplace, hot water boiler, or industrial furnace, the hot combustion product gases that are formed are called flue gases. Those gases are generally exhausted to the ambient outside air through chimneys or industrial flue-gas stacks (sometimes referred to as smokestacks).
The combustion flue gases inside the chimneys or stacks are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught/draft", "natural ventilation", "chimney effect", or "stack effect". The taller the stack, the more draught or draft is created. There can be cases of diminishing returns: if a stack is overly tall in relation to the heat being sent out of the stack, the flue gases may cool before reaching the top of the chimney. This condition can result in poor drafting, and in the case of wood burning appliances, the cooling of the gases before emission can cause creosote to condense near the top of the chimney. The creosote can restrict the exit of flue gases and may pose a fire hazard.
Designing chimneys and stacks to provide the correct amount of natural draft involves a number of design factors, many of which require iterative trial-and-error methods.
As a "first guess" approximation, the following equation can be used to estimate the natural draught/draft flow rate by assuming that the molecular mass (i.e., molecular weight) of the flue gas and the external air are equal and that the frictional pressure and heat losses are negligible: Q = C A 2 g H T i − T e T e \displaystyle Q=C\,A\,\sqrt 2\,g\,H\,\frac T_i-T_eT_e where:
Combining two flows into chimney: At+Af<A, where At=7.1 inch2 is the minimum required flow area from water heater tank and Af=19.6 inch2 is the minimum flow area from a furnace of a central heating system.
Gas fired appliances must have a draft hood to cool combustion products entering the chimney and prevent updrafts or downdrafts.[8][9][10]
A characteristic problem of chimneys is they develop deposits of creosote on the walls of the structure when used with wood as a fuel. Deposits of this substance can interfere with the airflow and more importantly, they are combustible and can cause dangerous chimney fires if the deposits ignite in the chimney.
Heaters that burn natural gas drastically reduce the amount of creosote buildup due to natural gas burning much cleaner and more efficiently than traditional solid fuels. While in most cases there is no need to clean a gas chimney on an annual basis that does not mean that other parts of the chimney cannot fall into disrepair. Disconnected or loose chimney fittings caused by corrosion over time can pose serious dangers for residents due to leakage of carbon monoxide into the home.[11] Thus, it is recommended—and in some countries even mandatory—that chimneys be inspected annually and cleaned on a regular basis to prevent these problems. The workers who perform this task are called chimney sweeps or steeplejacks. This work used to be done largely by child labour and, as such, features in Victorian literature. In the Middle Ages in some parts of Europe, a stepped gable design was developed, partly to provide access to chimneys without use of ladders.
Masonry (brick) chimneys have also proven to be particularly prone to crumbling during earthquakes. Government housing authorities in cities prone to earthquakes such as San Francisco, Los Angeles, and San Diego now recommend building new homes with stud-framed chimneys around a metal flue. Bracing or strapping old masonry chimneys has not proven to be very effective in preventing damage or injury from earthquakes. It is now possible to buy "faux-brick" facades to cover these modern chimney structures.
Other potential problems include:
Several chimneys with observation decks were built. The following possibly incomplete list shows them.
At several thermal power stations at least one smokestack is used as electricity pylon. The following possibly incomplete list shows them.
Nearly all this structures exist in an area, which was once part of the Soviet Union. Although this use has the disadvantage that conductor ropes may corrode faster due to the exhaust gases, one can find such structures also sometimes in countries not influenced by the former Soviet Union. An example herefore is one chimney of Scholven Power Plant in Gelsenkirchen, which carries one circuit of an outgoing 220 kV-line.
Chimneys can also carry a water tank on their structure. This combination has the advantage that the warm smoke running through the chimney prevents the water in the tank from freezing. Before World War II such structures were not uncommon, especially in countries influenced by Germany.
Chimneys can carry antennas for radio relay services, cell phone transmissions, FM-radio and TV on their structure. Also long wire antennas for mediumwave transmissions can be fixed at chimneys. In all cases it had to be considered that these objects can easily corrode especially when placed near the exhaust. Sometimes chimneys were converted into radio towers and are not useable as ventilation structure any more.
As chimneys are often the tallest part of a factory, they offer the possibility as advertising billboard either by writing the name of the company to which they belong on the shaft or by installing advertisement boards on their structure.
At some power stations, which are equipped with plants for the removal of sulfur dioxide and nitrogen oxides, it is possible to use the cooling tower as a chimney. Such cooling towers can be seen in Germany at the Großkrotzenburg Power Station and at the Rostock Power Station. At power stations that are not equipped for removing sulfur dioxide, such usage of cooling towers could result in serious corrosion problems which are not easy to prevent.
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