Candle Soot

[Reprinted from our old website]

Candles May Be The Cause Of Sooting

Candlemaker pays for soot damage
BROOKHAVEN, PA - We’ve all burned candles in our homes before. But there could be a hidden danger, and it doesn’t have anything to do with fire. News 10’s Tracy Davidson has the details on the ConsumerWatch.
Pat Morrison of Delaware County had a mystery on her hands that was destroying her home.
Right above the heater vent in these curtains, they were all black, Morrison said. I had no idea.
Her first clue was when she removed a hanger that had hung on a wall, and she saw the outline. On this vent, there were black cobwebs and white lampshades had cobwebs, she said. It just gradually got worse. Morrison had her heater inspected. It was fine. Then an engineer visited. I learned it was from the candles I was burning, Morrison said. Smoke will cover the walls but you won’t see it until you move a picture from the wall, said Paul Lutz, a chemical engineer. Lutz told Morrison the culprit was three candles on her living room table she’d been burning. But she’d only been in her house four months. That is why her insurance company decided to pay for the damage that totaled $18,000.
Everything needed to be dry cleaned, chemically cleaned or thrown out. This is atrocious for this to happen, Morrison said. I wouldn’t wish this on anyone. Morrison’s insurance company went after the maker of the candle: Candle-Lite. And in Delaware County Common Pleas Court, Candle-Lite agreed to pay $17,277 to the insurance company. News 10 contacted Candle-Lite. The company had no comment on the case.
So how can you check your own home for potential damage and how can you protect your home and belongings from candle soot damage? Find out Thursday, Oct. 28th 1999 on News 10 at 5.

( Minneapolis Star Tribune )
Q: I've noticed gray and black marks on the carpeting under doors, near table legs on walls and windows in my house. It's really noticeable in the winter. I have a fireplace but rarely use it, and it has been cleaned. What is causing these dark stains?
A: ''The likely culprit is the casual burning of candles in your home,'' said energy specialist Phil Smith of the Minnesota Department of Public Service. The stains you see are the result of accumulated soot from candle flames.
A burning candle may appear to be clean, but it isn't. Combustion that takes place at the flame is incomplete so candles produce tiny particles of soot invisible to the eye.
Smith said doubters should try this simple experiment: Hold a small mirror or sheet of aluminum foil a few inches above a candle' s flame for a minute or so. Look at the accumulation of soot on the surface.
The use of candles has proliferated in recent years. Especially popular are scented or aromatic candles, which produce the most soot. Research indicates that just a few candles a month may be enough to cause the stains you describe. The areas where you observe stains are significant clues. Sooty stains under doors, windows, at bottoms of walls and around table legs are telltale signs of air movement from naturally occurring convection currents in your home, Smith said. The heating system warms air, causing it to rise. When it cools, the soot is deposited.
Sometimes the soot will accumulate on walls right where the studs run, leaving shadow stripes called ghosting.
Smith said that accumulations in the winter are natural. The house is closed up, reducing the amount of ventilation and dilution of air. Also, end-of-the-year holidays often mean that more candles are being burned.
Keep in mind that there may be other sources for soot stains in a house. Any combustion device (water heater, furnace, gas log and cookstove) can produce soot, given the right conditions.
Have these appliances checked by a heating contractor to make sure they are burning clean and don't backdraft, even when household exhaust fans or the clothes dryer are in use.
Even automobile exhaust from an attached garage can contribute carbon to a house. For more information on testing for that, contact the Minnesota Department of Public Service's Energy Information Center at 651-296-5175 or 1- 800-657-3710.
Removing soot stains can be difficult, Smith said. If ordinary household cleaners don't work, you may have to use cleaners designed for petroleum stains.

Fixit // What causes those dark `ghosting' marks on walls? ( Minneapolis Star Tribune )
My wall studs are beginning to appear as dirty marks on the walls. What would cause this? I suspect it might have to do with the fact that I am a smoker or that I burn candles. If I repaint, will the problem reappear?
Unless conditions change in your home, the stains will reappear. The dark areas revealing the wall studs is a phenomenon called ``ghosting.'' It's part of a larger problem called sooting, where people notice that black, grimy dirt (not the typical dirt or dust) is accumulating on the walls, furniture, TV and computer screens, drapes, carpet and furnace filters in their homes. In some cases, only certain areas of the house are affected; in other cases, homeowners describe a generally dirty house. As the incidence of ghosting and sooting increases so does the concern of home builders and heating contractors, because they are being blamed for the problem. But they may not be to blame. Most experts agree that ghosting is caused by an accumulation of soot, but they don't agree on where it's coming from. The obvious suspect is candles. The use of candles has proliferated in recent years, especially the popular scented or aromatic ones. A burning candle may appear to be clean, but it isn't. Because the combustion that takes place at the flame is incomplete, candles produce tiny particles of soot invisible to the eye. The addition of fragrance oils to candles contributes to the sooting. Any combustion appliance (water heater, furnace, gas-log fireplace and cookstove) can produce soot, given the right conditions. In one ghosting case, a homeowner's water heater was found to be backdrafting. That means carbon-loaded exhaust from the burner flowed into the house instead of out of the house through the vent pipe. Even automobile exhaust from an attached garage can be a source of carbon or soot that can cause a dirty house. In one sooty-house case, the attached garage was found to be the source. Although the attached garage appeared to be completely separate from the house because the walls appear solid to the eye, they aren't to a gas. Garage air can move freely into the house through unseen cracks and penetrations. These natural drafts are loaded with minute carbon particles from the car's engine. No matter what the source of the soot, the problem can exhibit itself far from the original source because the forced-air heating system picks up the microscopic particles and circulates them throughout the house. The airborne particles are attracted to and coalesce on cooler surfaces, such as the stud area of walls. That area tends to be cooler than the surrounding wall because studs, unlike the wall next to them, are not insulated. The accumulation of the microscopic particles gradually turns the areas gray or black - ghosting. The soot particles also appear attracted to charged surfaces such as TV screens and some plastics such as coffee makers and counter tops. Eliminate the source of the carbon to solve the problem. In your case, it appears likely to be candle-burning. (Smoking generally deposits yellow residues, but eliminating indoor smoking is not a bad idea.) But don't forget about the fuel-burning appliances in your home. Have them checked immediately by a heating contractor to make sure they are burning clean and don't backdraft, even when household exhaust fans or the clothes dryer are in use. And install a digital electronic carbon monoxide detector right away. Like soot, carbon monoxide is a byproduct of combustion. Monitoring your house for carbon monoxide levels can protect your life and health as well as help detect the source of your sooting. If you take these steps and still have a sooting or ghosting problem, consider contacting a house diagnostician to determine the cause. Call the Minnesota Department of Public Service at 651-296- 5175 or 1-800-657-3710 for a list of diagnosticians. Visit its Web site at for information on house diagnosis and fuel-burning appliance checks.
For more information about ghosting and sooting, read an article at the Web site Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-9033, or e-mail Past columns are available at Sorry, Fixit cannot supply individual replies. Fixit appears every day except Friday.
Natural Life
May 24, 1999
Candles - A Burning Air Quality Issue
by Wendy Priesnitz, Editor
I’d never allow someone to smoke a cigarette inside my home or office. And yet, until recently, I never thought twice about burning candles...scented or otherwise, for romance or for stress relief. However, an increasing number of indoor air quality scientists are sounding the alarm about the ability of candles to emit pollutants like benzene, styrene, toluene, acetone and particulate matter. Some core wicks on imported candles have even been found to be made of lead.
Although in the past, specialists in environmental medicine have occasionally noted problems resulting from candle use, indoor air pollution and related health problems appears to becoming more common due to the popularity of scented and aromatherapy candles. If candles are not properly manufactured, or contain too high quantities of fragranced oils that are not suitable for combustion, the result could be an indoor air quality problem.
In the U.S., the National Association of Home Builders (NAHB) has been receiving an increasing number of reports about black soot deposition. A prime suspect is the increased use of candles and other indoor combustible materials including incense, potpourri and oil lamps. The problem is so severe that North America’s largest indoor air quality conference, held in Texas in mid April, featured a workshop that presented the latest research and case studies on the effects of black soot from candles.
Soot is a product of incomplete combustion of carbon-containing fuels, usually petroleum-based. The soot not only discolours walls and furniture, it can also contaminate your home’s ventilation system. Although the problems resulting from burning candles can be minimized, the basic problem is that candle flames must contain soot or they will not be bright. Soot is the source of the bright white/yellow light that candles emit. A flame without soot will burn blue, like the flame from a gas stove.
While little or no research has been conducted into the health effects of exposure to candle soot, studies into the risks of exposure to soot from diesel exhaust and factory emissions suggest candle soot can be harmful. Since soot particles are typically very small, they can potentially penetrate the deepest areas of the lung. Researchers caution that the very young, the elderly and those with respiratory diseases like asthma should avoid exposure to candle soot.
For more information, go to the website Candles and Indoor Air Quality at

Air-Vent Cleaning Specialists
Candles can be the Culprit!
Candles add to the warmth & atmosphere of a home. Some candles can contribute to an indoor air pollution problem by emitting particulate matter (candle soot) into the air. Candle pollution not only discolors the walls, ceilings and contents of a home it can also contaminate the ventilation system's ductwork. This is especially true of ducts constructed from fiberglass "duct-board". It appears that scented and/or aromatic candles are the worst offenders.
If the light colored fabrics in your home begin to look rather dingy or gray, if plastic items in the house begin to accumulate a dark film, if your electronic equipment has discoloration's especially around vents (i.e. computers, disc drives, etc...), if the television or computer monitor screen is covered with a thin dark residue that wipes off with a clean cloth (this film will appear darker than regular household dust on a clean cloth) you could have an IAQ (Indoor Air Quality) problem resulting from candle soot.
If you suspect a problem:
1) Stop burning candles immediately!
2) Check and/or change the filter in your H/VAC system, save the filter if it is more discolored than you would normally see.
3) Continue to change the filter more frequently than usual, you should observe a gradual lightening of each subsequent filter.
4) Depending on the extent of property damage you may want to contact your homeowners insurance and/or the candle's manufacturer.
5) You may also want to seek the advice of an Indoor Air Quality or Building Science Specialist.
6) If evidence is compelling towards candles causing the problems, you may want to contact CPSC (Consumer Product Safety Commission).
Do the Simple Inexpensive unscientific Test just to make sure!
Here is an easy but convincing (albeit not scientific) way to determine if candles are the cause of the soot deposition.
You'll need some of those thin, plastic disposable plates (White), not paper or styrofoam (although styrofoam will work, just not as well). Obtain several of the candles suspected of sooting. Light the candles in a confined area, for example a utility or bath room. Right after lighting the candles, separate the plates into 2 or 3 stacks (this will create a static charge) & place them near or around the burning candles. Let the candles burn about an hour (depending on the carbon emission rates of the candles being burned, could be as little as 10 minutes). If the candles are responsible for the soot deposition, you will notice a thin dark film collecting on the top plate of each stack. This type of soot has a strong attraction to plastics especially when the plastic is charged. This test is a relatively simple & compelling way to demonstrate to a homeowner or tenant that candles are responsible for the soot deposition in their home.
You should close or block all the H/VAC vents in the room where you are testing the candles to eliminate the H/VAC system as the cause of sooting and to prevent further contamination.
The emissions and soot produced by some scented and/or aromatic candles can not only damage a home, it's contents and the ventilation system but there is evidence that it also can present a health hazard from breathing sub-micron particulate soot emitted (sub-micron means < 1 micron). The EPA and the American Lung Assn. have determined that particulate matter 2.5 microns and smaller are the most detrimental to our health. The smaller the particle, the more dangerous, because it can travel deeper into the lungs. When particulate matter is breathed in, it can irritate and damage the lungs, causing breathing problems. People who have asthma or some type of lung disease are directly impacted by PM. The elderly and children are also especially vulnerable to the effects of PM. Many studies have shown links between PM and health effects. Increases in PM have been linked to decreases in lung function, increases in breathing problems and hospitalization, and early death. It is currently speculated (by Chemists, IAQ Specialist and other scientists) that the cause of this is due to candle manufactures adding more & more essential and fragranced oils (some of which are not even suitable for combustion) to candles in order to achieve a higher or more intense fragrance while burning. It also appears that many inexperienced & amateur candlemakers have jumped into the manufacturing of candles to capitalize on their current popularity without the proper training or expertise. The result is an abundance of inferior or poorly performing candles in a lot of homes.
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Candle issues
Posted by Cathy on February 19, 1999 at 07:35:20
If you have "unexplained" ghosting or soot deposits in your home pay a visit to the following bulletin board & see if any of these incidents sound alittle familiar...
The Home Owner's Candle Soot Damage Bulletin Board
Bear in mind candles are not the sole cause of soot deposits in a home; however, reports of soot damage from candle use are certainly on the rise. Other causes can include H/VAC & insulation problems, "puff-back", improper use/maitenance or malfunctions of fireplaces &/or chimneys, and even exhaust from an attached garage. But if all of these have been eliminated as the source & you are left scratching your head and use candles... it's quite possible that they are the cause.
Cathy Flanders
IAQ List Manager & Moderator
Fax: 972-527-6608
IAQ Listserve (to subscribe)
IAQ Listserve (to search archives)

 Candles and Indoor Air Quality
The Home Owner's Candle Soot Damage Bulletin Board


Candle Information and Tips
National Candle Assn. Home Page

Candle Information:
What is a candle?
What is a candle? A candle is a device for providing light or dispersing fragrance.
The body of a candle is comprised of a solid fuel source, usually paraffin wax. A wick runs through the center of the body of the candle from the bottom, extending out of the top. The wick, which acts as a fuel pump when the candle is burning, is generally made of cotton fibers that have been braided together.
Soot stained stone dishes found in ancient caves in France show that stone-age man used a crude candle/lamp to light the cave walls as he painted upon them. The saucer shaped stone appears to have held a piece of animal fat that could be set afire to give off light.
Ancient Egyptians were known to drip beeswax or tallow onto rush stems. They would set flame to the tip of these "Rush Lights" to provide them with light.
Today, we do not rely so much on candles for lighting our homes, except in the event of a power outage. Candles are now used for decorative or religious purposes, to create a mood with their hypnotic glow, their soothing fragrances please our sense of smell, and they often represent symbols of our personal faiths.
A candle is the light, the body, the soul of our modern imaginations.
You can obtain candles in a variety of styles. The main types of candle are as follows.

FLAME, glowing body of mixed gases undergoing the process of combustion . Flames generally consist of a mixture of oxygen (or air) and another gas, usually such combustible substances as hydrogen, carbon monoxide, or hydrocarbon. A typical flame is that of a burning candle. When the candle is lighted, the heat of the match melts the wax, which is carried up the wick and then vaporized by the heat. The vaporized wax is then broken down by the heat and, finally, combines with the oxygen of the surrounding air, producing a flame and generating heat and light. The candle flame consists of three zones that are easily distinguished. The innermost zone, a nonluminous cone, is composed of a gas-air mixture at a comparatively low temperature. In the second, or luminous, cone, hydrogen and carbon monoxide are produced by decomposition and begin to react with oxygen to form water and carbon dioxide, respectively. In this cone the temperature of the flame-about 590° to 680° C (about 1090° to 1250° F)-is great enough to dissociate the gases in the flame and produce free particles of carbon, which are heated to incandescence and then consumed. The incandescent carbon produces the characteristic yellow light of this portion of the flame. Outside the luminous cone is a third, invisible cone in which the remaining carbon monoxide and hydrogen are finally consumed.
If a cold object is introduced into the outer portions of a flame, the temperature of that part of the flame will be lowered below the point of combustion, and unburned carbon and carbon monoxide will be given off. Thus, if a porcelain dish is passed through a candle flame, it will receive a deposit of carbon in the form of soot. Operation of any kind of flame-producing stove in a room that is unventilated is dangerous because of the production of carbon monoxide, which is poisonous.
All combustible substances require a definite proportion of oxygen for complete burning. (A flame can be sustained in an atmosphere of pure chlorine, although combustion is not complete.) In the burning of a candle, or of solids such as wood or coal, this oxygen is supplied by the surrounding atmosphere. In blowpipes and various types of gas burners, air or pure oxygen is mixed with the gas at the base of the burner so that the carbon is consumed almost instantaneously at the mouth of the burner. For this reason such flames are nonluminous. They also occupy a smaller volume and are proportionately hotter than a simple candle flame. The hottest portion of the flame of a Bunsen burner has a temperature of about 1600° C (about 2910° F). The hottest portion of the oxygen-acetylene flames used for welding metals reaches 3500° C (6330° F); such flames have a bluish-green cone in place of the luminous cone. If the oxygen supply is reduced, such flames have four cones: nonluminous, bluish-green, luminous, and invisible.
The blue-green cone of any flame is often called the reducing cone, because it is insufficiently supplied with oxygen and will take up oxygen from substances placed within it. Similarly, the outermost cone, which has an excess of oxygen, is called the oxidizing cone. Intensive studies of the molecular processes taking place in various regions of flames are now possible through the techniques of laser spectroscopy.

Candle Tip #1:
Always protect the surface the candle rests on by placing the candle on a non- flammable holder to prevent either color or fragrance from bleeding into the surface. Brass candle holders can be especially sensitive to dark candle colors bleeding into their surface.
Candle Tip #2:
Place the candle in an area free from drafts. The first time you light the candle, allow it to burn until the liquid wax covers the entire top of the candle. This breaking in process insures that it will perform better and more evenly throughout the life of the candle. For pillars, plan on burning 5-6 hours on the initial lighting. With subsequent use, the candle should remain lit for a minimum of 3 to 4 hours each time. This will insure a clean and efficient burning cycle for the life of the candle.
Candle Tip #3:
To extinguish a candle, dip the wick into the liquid wax, using a non-flammable instrument. This little known technique eliminates smoking.
Candle Tip #4:
The wick is designed to produce a small black carbon cap at the top of the wick as it burns. This is normal as it helps radiate heat to the edge of the candle. You should not trim the wick nor touch it while it is cold! After extinguishing the flame, it is best to remove carbon deposits or other foreign materials from the liquid wax when possible.
Candle Tip #5:
Should your candle burn unevenly due to a draft consider this. Carefully push the wick towards the higher side. If this causes dripping, extinguish the flame, let it cool for an hour, then relight the candle. Repeat this practice a few times and the candle will repair itself.
Candle Tip #6:
To regain the color and luster of the non textured candle, simply buff with a soft cotton cloth or an old nylon to remove dust and small scratches like magic. This process revitalizes the candle's sheen. The heat from the candle burning tends to dull the finish but it can easily be regained with this simple maintenance tip.
Candle Tip #7:
Votive burning is fun, however the clean up of the dish is frustrating and time consuming. Eliminate this aggravation. Simply place four drops of tap water in the base of the votive dish prior to lighting. Once the votive candle is extinguished, allow the wax to solidify. Once solid, gently push on the wax and the contents should pop loose. Apply a small amount of Wax and Spot Remover, found on our Candle Accessories page, to eliminate the soot and wax buildup on the side of votive dish.
Candle Tip #8:
Floating candles can provide both a formal and informal setting for either a dinner party or a back yard picnic. Floating candles in a clear bowl creates an extra special lighting effect. Using distilled water eliminates mineral buildup on the side of crystal or glass, preserving its unique presentation of floating candles.
Candle Tip #9:
Translucent candles are most enjoyed after hours of burning. Their most impressive burns can be preserved by simply burning a small tea light in the base of the hollow for continued enjoyment of all translucent candles. Tea lights can be found on our Candle Accessories page, and you'll find lots of translucent candles on our Translucent Candles page.
Candle Tip #10:
Dinner candles, called Tapers, accidentally bumped can cause wax to be dripped on your table or table cloth. Decorative Bobeches come in many styles, colors and forms and eliminate unnecessary spills on your precious table or tablecloth. Bobeches are sold in the Candle Accessories section of the product catalog, and you'll find tapers on our Tapers page.
Candle Tip #11:
Wax removal can be simple with "Wax and Spot Remover" offered on the Candle Accessories page. This special product can remove stains and wax from cloth, wood, metal, plastic coated and painted surfaces. This special product turns disasters into simple distractions.
Candle Tip #12:
Many times the candle that is just perfect has a stem too large for its candle holder. Candle Sharpeners have eliminated most of this problem but many times it still needs some fine adjustment. Set the stem of the candle in a half inch of hot tap water (this softens the wax on the outside of the candle). Push the candle into the holder gently. The stem will custom fit to the candle holder. Repeat as necessary for a secure fit. Candle Sharpeners are sold in candle shops.

Candle-burning Tips
  • Keeping wicks trimmed to ¼ inch or less makes candles last longer and reduces black soot on jar
  • Burning votives in a good-fitting votive cup will make votives last longer
  • Use a spoon handle to push the wick to the center of the jar soon after blowing out candle to keep the wick in the middle of the jar. This will enable the wax to burn completely and last longer
  • When burning a jar for the first time, let it burn until the wax melts to the jar's edge; the candle will melt more consistently throughout its life
  • Burn votives in potpourri pots for tremendous fragrance
  • Use a spoon handle to push a three-wick wick toward the middle or outside of the candle to promote even burning
  • After extinguishing the flame on a three-wick while the wax is soft but not liquid, fold softened wax toward the inside of the candle to allow it to burn the next time
  • Never leave candles burning unattended


Candles May Not Be The Cause Of Sooting
Ruling Out Mold and Candle Soot
In staining cases that are not clear-cut, mold may be suggested as the culprit in sooting stains. But, black sooting stains are easily distinguished from stains caused by mold growth. Although the area in which a stain appears could be sampled and cultured (see "Sampling Stains for Fun and Profit," HE Sept/Oct '98, p. 12), and the sample would probably grow a few mold colonies, mold can quickly be ruled out. First, mold growth can be many colors, including white, black, various shades of green, or pinkish brown. Second, the outer edges of mold stains will look fingerlike or feathery. In contrast, sooting stains will be grayish black and will have a more uniform outer edge.
It is more difficult to rule out candle soot or car exhaust as potential sources. However, my experience is that candles are rarely the cause of sooting stains. Heavy candle use can contribute to staining near the candles, but it does not typically cause soot stains throughout the house. Furthermore, in many of the cases of soot staining I have seen, the owners did not use candles except for special occasions such as Thanksgiving and birthdays, and the stains clearly came from a different source.
If you are still unsure of the source of a sooting stain, one place to go for help is a laboratory. A lab can use scanning electron microscopy to determine, for example, whether a stain is caused by deteriorating insulation or by candle soot. Particles in stains from insulation material are significantly larger than particles from candle soot. Another way a lab can spot the difference is by running a chemical analysis of the material, checking for the presence of chemicals released by insulation off-gassing and degradation.
But, the clearest indication that deteriorating insulation in the air handler is the source of sooting stains is the way the stains appear in the house.
Staining Patterns
Often the stains first appear on the walls and ceiling, particularly on exterior walls. They concentrate on inside surfaces along the ceiling joists and wall stud boards, and especially around nail heads, where the surface temperature is lower than the temperature in the surrounding area.
This pattern is similar to that seen in smoke damage after a fire, because similar forces are at work. Because of the billowing effect of smoke and the airstream in a fire, soot and ash tend to concentrate and be deposited first at the juncture between the ceiling and the wall. Impaction and attraction, together with gravity, are the main forces involved in this characteristic staining deposition. Stains also may outline furniture or other objects on the floor, and windows or pictures on the walls.
Impaction is a physical force that plays a key role in particle deposition. The air in a building is fluid and moves through the occupied space in a distinct, usually circular, pattern. typically this is a pattern of convection, in which warm air rises in the middle of the room, cools while moving toward the walls, and falls again. When the air turns to go down a wall, some particles in the airstream, the larger ones, keep moving outward instead of down. Because of their larger size, and thus greater momentum, inertia keeps them moving in a straight line until something stops them and the particles impact on the wall's surface (see figure below).
Attractive Forces
The attractive forces include static charge and "thermophoresis." Static charges--and therefore, sooting stain depositions--often occur on the television screen, plastic pipes, plastic dishes, vinyl window and door casings, and plastic appliance cases. They are also often seen inside the refrigerator, especially on the egg-keeper and butter door. This is due to the fact that many plastic items have an electronic, or static, charge buildup on their surfaces because of the chemical nature of the material and the way the item is manufactured. Polyethylene and polypropylene are two plastics that typically build up static charges.
Static charge results when there is a an overall net possitive or net negative charge on the surface of an item. This happens when two surfaces are pressed tightly together and then pulled apart, or from friction. One of the surfaces will have more electrons (net negative) and the other will have more protons (net positive). You can also create ions from air molecules when the air is passed through an electric field or a magnetic field. A classic example of static charge is the "shock" a person gets when they touch a metal object. The person has "discharged" themselves with a micro-lightening strike.
Opposite charges attract whether it is the surface it was just removed from or a different surface. If you have a surface that is positivly charged and you have another surfac that is negatively charged, they tend to be attracted to each other. The result is a dirt accumulation on the other surface.
Thermophoresis, or "thermal precipitation," is a physical settling effect in which particulates in the air stream plate out on surfaces that are colder than the airstream. Different materials acquire or lose heat at different rates; therefore, some items will always be colder than other surrounding items. Particles will "stick" to colder surfaces and will become noticeable as a sooty stain.
Soot staining often outlines such things as furniture, pictures, and window treatments, and may be found on the top side of ceiling fan blades when the fan is turned off--anywhere there may be a pocket of still air. This is because the still air allows the particulates time to drop down, pulled by the Earth's gravity, and settle on the closest surface.

RE: candle soot!?!
Posted by: Christy - IA ( on Thu, May 27, 99 at 16:57
Don't be so sure it is candle soot. Do any of you have a new furnace by chance? The furnace could be the culprit, not the candles. We have a new furnace and soot - and are in the process of having the soot tested because an environmental specialist we contacted said "NO WAY IS THIS CANDLE SOOT". Of course, the furnace manufacturer says it is.
To make a really long story short, the environmental company says that many of the new furnaces that are being manufactured use a particular type of insulation in the furnace wall, the insulation fibers are being burned in the furnace, in turn the soot from those burnt fibers is what is showing up on homeowners walls.
The soot from the fibers leaves a specific residue that candle soot doesn't. There are some home owners on the East Coast that are sueing furnace manufacturers over this very issue.

RE: candle soot!?!
Posted by: Kenny C. ( on Thu, Jun 3, 99 at 11:44
I attend seminars on IAQ and this has become a hot topic. It turns out there are many factors that affect the soot generation by candles and its ditribution by a heating or airconditioning system. This person may have a compounded problem due to air intake location, the type of filters used and any air leaks between the filter and the indoor unit. These are only a few things to consider. My first area to inspect is the connection between the filter and the unit, any leaks would cause unfiltered air to enter into the fan. For soot to come out of the supply grill the following path was traveled. The soot in the air went through a filter or around it, through the blower, past the heater, through the evaporator coil, through the supply plenum, through the supply duct, and lastly through the supply grill. While on this trip it stayed airborne and did not stick to any surface. This does happen, but the concentrations of soot are very high for very long periods of time. If the return air duct is air tight and a 40% pleated air filter is used I feel confident the system will not take in any soot.

RE: candle soot!?!
Posted by: Bill Drake ( on Thu, Jun 3, 99 at 11:44
I must agree with Marian about the insulation in furnaces. The portion of insulation around the heat exchanger is fiberglass with aluminum foil facing the air stream so that the insulation is encapsulated between the casing and the AL.foil. Some furnaces have insulation within the return air compartment. This is black matt faced designed by the insulation manufacturers just for such applications and has been used in the HVAC industry from the late 1970's. Like Marian said until the last two years in paticular, sooting was not an issue. It would therefore seem logical not to blame the insulation which has been used in the marketplace by HVAC units for many years.

If you have had any similar problems or have information regarding this issue, please post a comment here.

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