Indoor stains in buildings traced to black or dark thermal tracking or ghosting lines:

Building Air Leaks & Heat Loss Points. This article describes & diagnoses the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, (also called ghosting or ghosting stains or thermal bridging stains), building air leaks, and building insulation defects.

Often these stains are mistaken for toxic indoor mold.

What are Thermal Tracking, Ghosting, Sooting, Thermophoresis, Electrostatic Deposition, Plating-Out Stains

Ghosting Marks: what causes those dark stains on building interior walls & ceilings? Photos & text identify thermal tracking, thermal bridging, air bypass leaks, insulation defects and air movement in buildings.

Thermal tracking stains or dark thermal ghosting stains (also called thermal telegraphing stains) indoors indicate building air movement, air leaks, and points of heat loss which increase home heating or cooling cost.

Here we explain how to recognize poorly insulated building walls or ceilings and how to pinpoint building air leaks.

We provide a photo-guide to common indoor ceiling and wall stains and what they mean.

Also discussed:

Why & how thermal tracking and ghosting stains could indicate very dangerous carbon monoxide hazards in a building.

Soot from natural gas, LP gas, or oil burners - sooting gas appliances are dangerous.

Thermal tracking marks can indicate thermal bridging: locations of building heat loss. We include this definition

of THERMOPHORESIS

[Click to enlarge any image]

Article Series Contents

• AIR MOVEMENT in BUILDINGS - When, where, how & why air moves in buildings
• THERMAL TRACKING BRIDGING GHOSTING - home
  • DEFINITION of THERMAL TRACKING
  • EIGHT INTERACTING FACTORS CAUSE GHOSTING
  • AIR VELOCITY & MOVEMENT PATTERNS
  • COMPOSITION of DARK GHOSTING STAIN PARTICLES
  • GHOSTING STAIN INSPECTION
  • GHOSTING DARK STREAKS or LINES: CAUSES
  • GHOSTING DARK RECTANGULAR STAINS: CAUSES
  • GHOSTING DARK STAINS from AIR LEAKS
  • GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS
  • GHOSTING STAINS on WALLS
  • STAINS CANDLES FIREPLACE WOODSTOVE
  • STAINS DIAGNOSE IAQ PROBLEMS
  • STAINS INDICATE SAFETY CONCERNS
  • STAINS MISTAKEN for GHOSTING
  • THERMAL TRACKING MOLD GROWTH
  • THERMAL TRACKING REMEDIES

What is Thermal Tracking & Why does Thermal Tracking or Thermal Staining Occur Indoors?

What is thermal tracking or ghosting and what causes it?

Thermal tracking or "soot tracking" such as shown in the photo at left and also in the photograph at the top of this page may be found wherever moisture condenses on cool building surfaces.

Warm moisture-laden air touches the cooler surface of a building wall or ceiling, giving up some of its moisture to the surface as condensation.

See DEW POINT TABLE - CONDENSATION POINT GUIDE for details.

That makes some areas on an indoor surface slightly more damp than others.

As air moves by natural convection through the building, it typically flows up walls and across ceilings.

Airborne debris in the air, particularly soot such as that left by airborne house dust, by a heating system that needs service or by burning candles (scented candles may be more of an IAQ issue), or by cigarette smoking, adheres more to the damp surfaces than to others, leaving black marks or "tracks."

Black thermal tracking stains may appear on interior walls and ceilings, not just on cool exterior building walls. It is also possible that an interior partition wall may be conducting heat out of the building through convective loop heat losses as well.

See CONVECTIVE LOOPS & THERMAL BYPASS LEAKS.

While most people don't use the terms thermal tracking or ghosting with great precision, it is useful to understand how particular stain patterns are laid down in a building. Understanding the location, shape, size, and intensity of a stain on a building wall or ceiling can help us understand how a building works, its energy efficiency, and the quality of its indoor air.

To track down and fix thermal tracking stains you will need to fix air leaks and provide insulation where it's missing or inadequate.

Eight Interacting Factors Determine When & Where Stains Appear in buildings

[Click to enlarge any image]

Thermal tracking or "ghosting" is the deposition of house dust and debris onto walls and ceilings in patterns caused by a combination of air movement, interior moisture, and in some cases, a source of high levels of particles.

The rate of particle deposition that ultimately forms these dark indoor stains depends on several variables including the following factors that I list alphabetically rather than in importance for the typical homeowner. I include links to related articles that go into greater depth but I suggest wading through this one in its entirety first.

Conflicting variables are at work in the deposition of soot and debris on building surfaces. Here are some examples:

• More dust where more air moves: 
  
  Building surfaces exposed to more air movement are exposed to more airborne dust and debris - so may become stained.
  
  This phenomenon is most apparent where house dust and debris are deposited on and around air return registers in buildings. Where the air filtration system is not effective or the duct system is dirty, dust and debris are also deposited on and around warm or cool air supply registers.
  
  (This dust is most often harmless house dust comprised mostly of skin cells and fabric fibers.)
• Less dust where more air moves:
  
  Building surfaces exposed to more air movement might, however, also be kept warmer and more dry due to that same movement, so the same areas may become less stained than their neighbors.
  
  This phenomenon is most apparent in a building closet, or on a wall behind a picture or behind drapes, because less air moves over those surfaces, leaving the surface cooler, exposing the surface to higher moisture condensation, and thus causing more house dust (or soot) deposition than in other areas.

Let's look briefly at thermal tracking's causes, arranged alphabetically rather than in order of impact on the formation of indoor stains on ceilings & walls, or thermal tracking / ghosting:

Eight Factors that Determine the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls

1. Air velocity:
   
   the speed of air movement over a building surface affects the rate of deposition of particles on the surface.
   
   Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.
   Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls.
   
   This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.
   See
   
   AIR VELOCITY & MOVEMENT PATTERNS in this article (below) for details about this factor
   
   
   For help in studying this parameter
   
   
   See AIR FLOW MEASUREMENT CFM
   and also
   
   See AIR MOVEMENT in BUILDINGS
2. Carbon Dioxide CO₂ level:
   
   in public buildings or offices or your well-attended church or synagogue where the number of occupants might increase the indoor CO₂ near 2000 ppm, increased carbon dioxide levels combined with high indoor moisture can encourage the deposit of white deposits of calcium bicarbonate.
   
   This is a particular concern in museums or at the Sistine Chapel, as Grabon (2015) explains, noting that for the Sistene Chapel the HVAC system has been designed to keep the CO₂ below 800ppm. You won't see these deposits in a normal residential structure.
   
   See this related article:
   
   ARTWORK MOLD CONTAMINATION
   
   and also
   
   see TYPICAL CO2 LEVELS
3. Ceiling or Wall temperature:
   
   the interior surface temperature and its variation from the temperature of room air determines if condensation will occur on those surfaces at all.
   
   Warm air carrying moisture will increase condensation on the cooler surfaces. If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.
4. Dew point temperature:
   
   when the ceiling or wall surface temperature is below the dew point temperature moisture will condense on the surface.
   
   The moisture collecting on those surfaces then causes more airborne particles to adhere. Keeping a wall temperature close to the nearby air temperature minimizes particle deposition. The dew point temperature is the air temperature at which the air is saturated: it can't hold any more water.
   
   See DEW POINT TABLE - CONDENSATION POINT GUIDE
   
   We explore define dew point temperature and relative humidity (RH) and we explain the relationship of temperature and RH in a separate article
   
   at DEW POINT CALCULATION for WALLS
5. Non-Particulate airborne pollutants:
   
   other non-particulate pollutants also affect building surfaces, particularly sulfur dioxide (SO₂₎, as in interiors where the RH is high, the moisture in air combining with SO₂ can actually form sulphuric acid that in a museum or where there are frescoes or other important surfaces, the acid may attack these materials.
6. Particle composition & level in the air:
   
   soot, burning candles, fireplaces, pets, increase the particle level. In public buildings particles also enter the building from people, not just their pets, but also on shoes, clothing, carried items.
   
   For protected areas such as museums and indoor frescoes, Grabon (2015) cites an HVAC design level that keeps the indoor dust concentrations (particle size range ParticulateMatter PM 2.5 microns) below 0.003 µg/ft³ (0.1 µg/m³). That's a dust control level enormously more stringent than you'd seek for a normal residential space.
   
   For example the US EPA's 24-hour fine particulate standard is 35.0 µg/m³ - the same particle level as the output air from some of the best carpet vacuums cited by the Carpet and Rug Institute (CRI).
   
   See
   
   AIRBORNE PARTICLE COMPOSITION in this article (below) for details about this factor
   
   
   Also see AIRBORNE PARTICLE COUNT VARIATION CAUSES
7. Relative Humidity:
   
   Rh as a Factor in the Development of Indoor Stains on Building Surfaces: If indoor humidity is excessive (say regularly over 50 or 55% RH) we may be encouraging both staining from soot and house-dust deposition as well as mold growth in a building.
   
   Also we may be inviting excessive levels of dust mite activity which in turn increases the level of allergens in the building.

   That is because higher humidity indoors provides more moisture to condense on cooler building surfaces whenever the temperature of a building surface reaches the dew point.
   
   Stated another way, if a building has low indoor humidity, the amount of moisture available to condense on cool surfaces is less, so the rate of thermal tracking or soot deposition on those surfaces is less - at least due to this factor.

   See DEW POINT TABLE - CONDENSATION POINT GUIDE for details about the dew point and how to measure or calculate it for a building area or surface.

   Also see HUMIDITY CONTROL TO PREVENT MOLD

8. Wall surface temperature 
   
   and its variation from the temperature of room air: warm air carrying moisture will increase condensation on the cooler surfaces.
   
   If you can keep the wall surface temperature always 18F or 10C above the dew point temperature, there will be no condensation on your walls. You can do this by managing room temperature or by managing the RH of the air in the room, or both.

Even if the building humidity levels are low, high levels of indoor dust and debris can still lead to indoor stains and thermal tracking marks. Other factors that may be at play include electrostatic attraction or thermophoresis, discussed later in this article.

Air Velocity & Patterns vs the Level of Thermal Tracking or Dust Particle Deposition on Ceilings & Walls

Air velocity & air movement patterns: the speed of air movement over a building surface affects the rate of deposition of particles on the surface. Faster air movement brings more particles in contact with the surface where depending on other factors, they may plate out or stick.

Air movement in buildings occurs at different velocities in different areas even within the same room, depending on the location of incoming air sources (such as an air conditioning or warm air heating vent) and on sources of heat that cause convection currents in the room or even inside building exterior walls or interior partition walls.

This variation may explain why we see dark thermal tracking stains above heating radiators and baseboards even though those are not forced-air heating systems.

For more help also

See AIR FLOW MEASUREMENT CFM

and
See AIR MOVEMENT in BUILDINGS

Air Movement Patterns as Factors in the Development of Indoor Stains on Building Surfaces

Specific and non-uniform moment of building air can lead to uneven soot or house dust deposition on building surfaces, and thus will cause stains and dark areas that are non-uniform . Surfaces across which more building air moves are exposed to a greater volume of air and thus a greater volume of dust particles.

Electrostatic deposition,  plating out and thermophoresis 

of ultra-fine airborne particulate debris also explains black stains, sooting, or ghosting, as has been pointed out by Roger Hankey and Joe Lstiburek and others.

Electrostatic deposition refers to the sticking of particles to a surface due to a difference in electrical charge between the particle and the surface.

We often observe heavy electrostatic deposition of indoor dust and debris on building walls, ceilings, and other surfaces (most visibly on walls and ceilings) in homes where an ion generator is being used in the belief that it is "purifying" indoor air.

A friend in Rhinebeck, NY cranked up her indoor air ionizer to reduce the level of dog dust in her home - she boards as many as 15 dogs at a time in her home.

Indeed, over just a few months, we observed empirically that there was an increase in the rate of sooting on indoor painted walls and ceilings. Particles were probably sticking to other surfaces as well, but they were less visible.

Watch out: excessive use of indoor air ionizers, especially improperly adjusted, can produce harmful levels of ozone indoors.

See OZONE MOLD / ODOR TREATMENT WARNINGS.

Brownian motion, or pedesis,

describes the random movement of particles, in this case airborne particles, perhaps impelled by energy from heat, light, or ambient air current, possibly plating out by impact collision with building surfaces.

Thermophoresis 

is a term used by some IH professionals to explain the combined action of particle impact, moisture, and adhesion to surfaces, and is explained below

at Thermophoresis as a Factor in ... Indoor Stains

But unlike common thermal tracking, particles that are deposited on building surfaces by electrostatic deposition, brownian motion, or thermophoresis may be expected to occur without the presence of uneven surface moisture, temperature, and thus classic thermal tracking features.

• are likely to be more uniform in the areas they cover than particles deposited by thermal tracking
• will not specifically map building wall studs, nails, or other cooler or more moist building surfaces

Filtration and Thermal Tracking or Ghosting on Carpeting 

and Possibly other Fabrics such as wall curtains can indeed explain dark stains on carpeting under doors and at room perimeters where there may be air leaks.

Lstiburek offers a compelling explanation that airborne dust and debris (of all particle sizes) is filtered out by the carpeting or other fabric surface over which air may be passing.

So a difference in air pressure between rooms (someone is running an exhaust fan for example), or air leaks at the perimeter of a floor (construction is leaky and cold air is rising from a crawl area or from outdoors into the occupied space of an upper floor,for example) indeed can deposit dark black stains on carpeting.

Airborne Particle Composition in Black Stains Found in Thermal Tracking or Electrostatic Deposition

Our photo of black vertical stripes on walls of a home was contributed by an InspectApedia reader who asked what they were. Because the lines so neatly map wall stud spacing these are almost certainly thermal tracking or ghosting marks explained in this article.

But what makes up the dark stains? Pretty much regardless of the various mechanisms that cause airborne particles to deposit on ceilings or walls where they form dark stains or "sooting" or "ghosting" on interior building surfaces, the actual particles that can be expected to make up the stain include the following:

• Soot and combustion products 
  
  produced most often by cigarette smoking (brown wall stains), candles, especially scented candles or incense, soot from poorly-maintained oil fired heating appliances, soot from improperly-operating (and dangerous) gas-fired heating appliances, smoke particles from fireplaces or other indoor combustion activities (burning food on the stove?).
  
  See OIL BURNER SOOT & PUFFBACKS
  
  and GAS BURNER Flame & Noise Defects.
• Particulates from pyrolysis in buildings:
  
  Lstiburek opines that pyrolysis of lint in clothes dryers and similar activities may also produce ultra-fine particles plating out on walls as soot or ash. Indeed, pyrolysis is a chemical process that through exposure to heat causes organic material decomposition that in turn lowers the combustion point of a material.
  
  And as pyrolysis changes the properties of a material it can indeed release gases, liquids (tar) and char (solid residue) that could be deposited on building surfaces. just below.
  
  Details are in a separate article
  
  at PYROLYSIS EXPLAINED.
• Thermophoresis 
  
  might be a factor in the development of indoor stains: when condensation occurs on a building surface at any level that makes that area more damp (and thus sticker) than its neighbors, the temperature and humidity-related particle deposition described above is almost certainly occurring in any building, and will be more noticeable in a building with high levels of airborne particulates and dust.
  
  

  IAQ consultant Steven Temes, an industrial hygienist and microbial consultant points out, ultrafine carbonaceous particles (such as candle soot) also accumulate on the colder surfaces due to a little known physical phenomenon called thermophoresis. 
  
  This has to do with the driving force of the particle motion being its kinetic energy (when not overwhelmed by air currents) and the movement of the particle toward the cold surface, where it "plates out", adhering to the surface.

  If the particle has an electrical charge (such as in a home where ozone generators or negative ion generators are in use) this plating-out process will be significantly increased. If you are using an ozone generator as an "air purifier" indoors, be sure to
  
  see OZONE AIR PURIFIER WARNINGS
  
  and also OZONE HAZARDS.

• Mold growth
  
  in patterns on ceilings or walls is uncommon but in rare cases mold growth patterns may follow thermal tracking patterns on those surfaces.
  
  See THERMAL TRACKING MOLD GROWTH for an example of this less-common mold-pattern.
• Other very fine airborne dirt 
  
  or soil particles such as soil particles, organic particles, enter the building on animals, people, objects and airborne from nearby processes such as construction, incinerators, even simple vehicle traffic. Soot from diesel engines of some buses or other vehicles is a significant airborne particle source in many cities.
• Skin cells 
  
  from building occupants (humans, other animals) will almost certainly be present, as these are a common ingredient in house dust
• Fabric fibers,
  
  in very small fragments may be present as these too are a common ingredient in house dust

What particles are unlikely to make up the black stains associated with thermal tracking or ghosting?

In our forensic lab we have examined surface particles from literally thousands of building samples, including soot stains from dark or dirty surfaces, leading to the opinion about thermal tracking and plating particle makeup.

Other indoor particles that may be common in buildings and are cited by some other writers including some building scientists (Lstiburek) are less likely to be found in the black or dark indoor surface stains we describe here, for the reasons we list below. Some of these less-likely sometimes-airborne particles that have been posed as candidates for participating in the thermal tracking or ghosting festival include:

• Concrete dust:
  
  too heavy, does not remain airborne over long periods, typically gray or white
• "Dirt" needs to be defined.
  
  Generic "dirt" formed of soil particles or road dust and debris are found at low levels in indoor air samples and are normally too heavy to remain airborne or appear in thermal tracking on walls and ceilings. Dirt will, of course, be present at high levels in carpeting.
  
  Dirt as black smudges on walls may deposited by thermal tracking or by humans or animals in the building - the diagnosis of which black stain or dirt deposition source is at fault: creatures vs. airborne house dust lies in the deposition pattern.
• Drywall (gypsum board) or plaster dust:
  
  these particles are typically white or gray and are easily identified in the microscope. They do not normally look gray or black on building surfaces.
• "Gas smoke" -
  
  this is an undefined material; burning LP or natural gas produces carbon dioxide and water vapor, both colorless.
  
  Watch out: If LP or natural gas fuel are producing visible smoke (or black soot) a very dangerous condition exists risking fatal carbon monoxide poisoning - shut off the equipment and consult an expert immediately; if smoke alarms or carbon monoxide alarms are sounding, leave the building.
• "Insulation smoke" -
  
  is also an undefined term. Fiberglass and similar building insulation particles are rarely found on walls and ceilings in dark stained areas, though insulation particles are regularly found in indoor air and on horizontal surfaces in settled dust. Insulation fragments are too large to be part of the thermal tracking deposition process and are not black.
• Lint,
  
  properly referred to as fabric fibers, is rarely found in thermal tracking stains (too large, heavy) but is very common in indoor horizontal surface dust.
  
  However very fine lint particles, even without pyrolysis, may join other house dust particles to be deposited on building walls due to the thermal tracking process we describe here.
  
  See PYROLYSIS EXPLAINED
• Mold does not usually grow in regular patterns like those shown in thermal tracking, but it might:
  
  mold spores can include particles down around the 1micron level (though most are larger).
  
  While we find mold growth on indoor surfaces where there have been leaks or other mold-conducive conditions, we do not normally find high levels of mold spores in surface samples from vertical surfaces (walls) or overhead ceilings in buildings that are not themselves already mold contaminated.
  
  See THERMAL TRACKING MOLD GROWTH for an example of this possible, but less-common mold-pattern on a ceiling
  
  Mold growth on walls may also follow moisture gradients and variations, but usually these are not in the same pattern and certainly not in the same texture as thermal tracking of dust and soot.
  
  Details are at MOLD APPEARANCE - WHAT MOLD LOOKS LIKE

Brownian motion? As building scientist Joe Lstiburek points out, brownian motion also can cause particle adhesion to indoor building surfaces by the simple mechanism of mechanical impact of the particle with a building surface.

But particles that remain airborne in Brownian motion are ultra small and thus less likely to include most of the particles listed above.

Visual Inspection by an Expert can Usually Sort Out the Causes of Building Stains

Conceptually, the deposition of dust, soot, or debris on building surfaces out of moving air in buildings (as opposed to caused by animals or people touching surfaces) is a complex linear equation that is weighing different and conflicting factors.

Luckily, the visual inspection of the stained areas, combined with inspection of the building for moisture problems, insulation and ventilation problems, or for soot and debris sources, can normally identify the dominant effect and can with confidence conclude the cause and thus suggest the cure for these stains.

Thermal Tracking Lines Might be Mold?

Beware that on occasion the leaks and moisture in a building that contribute to thermal tracking may have created a mold problem either on the same surface or somewhere else than in the black thermal tracking or soot marks you see on walls and ceilings.

The wide dark lines on this apartment ceiling appeared after the space was left closed, unattended for months while there was a moisture source: an open refrigerator.

The same construction details (placement of framing or construction of a ceiling using small plasterboard panels) that cause variations in ceiling temperature and and moisture occurring in patterns as those that cause ghosting stains comprised of house-dust or soot might also, in less-common cases, produce mold growth.

MOLD / ENVIRONMENTAL EXPERT, HIRE ? provides assistance in deciding if you should hire a mold investigator.

Because some clients have on occasion sent samples to our mold test lab that really should not have been collected, much less looked-at, we recommend that you review the photographs in these articles to see if the black stains you see are something other than mold.

A method for collecting surface or settled dust, debris, or suspected -mold samples is detailed

at TAPE TEST for PARTICLES

When investigating a building for a mold problem, you can save mold test costs by learning how to recognize Stuff that is Not Mold or is only Harmless Mold but may be mistaken for more serious contamination - save your money

Question:

I would be very grateful of i could have your professional opinion on a mould/mildew problem. [See photo above and second photo just below]

The apartment was closed for several months and refrigerator door accidentally opened wich cause a rise in himidity and when i returned the bedroom ceiling was looking like in the attached photos.

I didnt take immediate action and lived in there for several months and now I feel really stressed about the whole thing.

The ceiling is constructed of cement and the outer layer is plastic paint.

There is no penetration in the paint and it is really easy to clean as if it were soot.

Any idea what it might be? - Anonymous by private email 2021/06/27 (Greece)

Moderator reply: mold stains on the ceiling

From your second photo [just above] that looks like it may indeed be mold.

Watch out: fight that panic; the anxiety around a topic like this may be even worse for your health than whatever is on the ceiling. But yes the ceiling needs to be attended-to: you'll want to clean the surfaces thoroughly.

1. Clean the surfaces
   
   (remove the mold) as much as you can; stains in the surface of wood will be harmless.
   
   Any household cleaner may work if this is a hard plaster surface and if you are confident that the mold doesn't penetrate th surface of the paint.
   
   Normally for more than 3 square meters of moldy surface you'd hire a professional. Because of the cost involved, though I'm reasonably confident that we're seeing mold growth, you might want to confirm that with a simple adhesive tape test of the dark material to confirm that it's a mold.
   
   An easy and inexpensive way to do that is at TAPE & BULK SAMPLING & TESTS for MOLD
2. Seal the surfaces (optional)
   
   with a fungicidal sealant paint before finish-painting
3. Fix the cause of mold growth:
   
   leaks and moisture (perhaps just the refrigerator, but also possibly a lack of building insulation)

Please see ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD

Also see PLASTER BULGES & PILLOWS for a possible explanation of why those dark lines appear on the ceiling in that particular pattern and spacing.

Why does Thermal Tracking or Ghosting Often Appear in Streaks or Lines?

Location & spacing of building framing members - key in recognizing true ghosting stains.

Indoor stains can help find the location and spacing of wall studs or ceiling joists.

When ghosting stains are spaced at regular intervals the stains are usually due to the deposition of building soot and dust on cooler surfaces associated with the greater heat loss at studs or ceiling joists than occurs at the insulated cavity between these framing members.

Typically these dark lines mark the cooler wall or ceiling surface areas where studs or joists are present; you may also see dark spots in lines marking drywall nails or screws for the same reason.

Details about the formation of ghosting lines on walls or ceilings have been moved

to GHOSTING DARK STREAKS or LINES: CAUSES

In a conventionally-framed wood structure, wall and ceiling framing is typically spaced on 16" or 24" centers, and thermal tracking will tend to cause dust or soot to adhere to the interior surfaces at these locations. You can see this phenomenon in our ceiling stain photo (left).

This interior black wall stain pattern is particularly easy to identify on walls -

see WALL THERMAL TRACKING STAINS

Observing the spacing between these stains can also tell us how a building has been framed and where the framing members are located.

Causes of Dark Spots, or Rectangular Stains on Ceilings or Walls

Identify areas of poor or missing insulation

The presence of thermal tracking stains mapping rectangular areas (photo above) between building framing members often means that the wall or ceiling where these stains occur are poorly-insulated.

The dark rectangular stains on the kitchen ceiling shown in this reader-contributed photograph probably mark areas of insulation voids in the ceiling.

Details about rectangular stains on walls & ceilings have been moved

to GHOSTING DARK RECTANGULAR STAINS: CAUSES

Watch out: the dark rectangles around recessed ceiling lights is indeed ghosting, and may mean that insulation was kept back from these pot lights.

However for fire safety, unless a ceiling light is rated DCIC (Direct Contact with Insulated Ceiling) it cannot be covered by insulation or you'll create a fire hazard.

Role of Building Air Leaks in Thermal Tracking Marks at Interior Ceilings or Walls

This discussion has moved to GHOSTING DARK STAINS from AIR LEAKS

Thermal tracking stains may appear at the top of the wall and extend onto the ceiling surface such as shown in this photograph.

These ceiling stains probably mark the location of ceiling joists (where the in-room ceiling surface temperature was kept a bit cooler since these locations in the ceiling cavity are occupied by a wood joist rather than by insulation).

Black Stains on Insulation: Air Bypass Leaks

This discussion has moved to GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS

How to Use Indoor Stains Like Thermal Tracking to Diagnose Building Air Leaks, Insulation Defects, and Indoor Air Quality Problems

This discussion has moved to STAINS DIAGNOSE IAQ PROBLEMS

 

More Indoor Stains Identified as Ghosting or Bridging

A careful examination of the location of indoor stains permits the observer to use thermal tracking or soot marks on building walls or ceilings as an indicator of possible excessive (seasonal) interior moisture or other potential indoor air quality concerns.

Dark stains on building interior walls may appear in other patterns and could be from other causes - we provide photographs, description, diagnosis, and advice for many of these indoor stains in this article series. Let's start with another example

of THERMAL TRACKING BRIDGING GHOSTING so that we an distinguish these stains from others listed below.

Reader Question: pictures from our living room.

... these stains are getting worse ... my husband does notice that insulation seems to need work.... Everyone keeps saying it cant be healthy ... I'm worried - K.C. 4/4/2014

Reply: how to recognize thermal tracking or ghosting stains in buildings

There is no doubt that we are looking at thermal tracking or "ghosting" - deposits of dust and soot on cooler, more humid areas of ceilings in your home.

These are not themselves a particular health concern but the conditions that cause thermal tracking, if they involve high indoor moisture levels, particularly if that moisture comes from a damp or wet basement or crawl space, could be a subtle clue that there is a hidden mold problem in the building.

Watch out: if the building soot source that is providing material for the black ghosting stains in your photos were an improperly-operating heating system or gas fired appliance dangerous conditions could be present such as carbon monoxide.

In our separate article on recognizing indoor stain types

IAQ DIAGNOSIS via THERMAL TRACKING STAINS I discuss all of your photos in more detail.

We explain this phenomenon beginning at the start of this article and we offer some remedies

at THERMAL TRACKING REMEDIES.

Stains that are NOT Thermal Tracking, Bridging or Ghosting

This discussion has moved to STAINS MISTAKEN for GHOSTING

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-10-27 by InspectApedia Publisher - be sure you have working smoke and carbon monoxide detectors

@Edits For Me La,

Adding:

Watch out: we notice that someone has removed a ceiling-mounted smoke detector. That's an important safety device that should be replaced right away.

Was that detector removed because some soot or smoke source in the building was causing it to sound off ?

If so, that's another serious safety warning that should not be ignored.

On 2023-10-27 by InspectApedia Publisher

@RRP,

Your photo, discussion, and our reply are in the page bottom reader Q&A of our ceiling stains diagnosis page

https://inspectapedia.com/interiors/Ceiling_Stain_Diagnosis.php

On 2023-10-27 by InspectApedia DF (mod)

@RRP,

Please read the information above on this page, as well as our responses below to other readers. That will be more thorough and informative than us trying to rewrite it all here.

On 2023-10-27 by InspectApedia Publisher

@RRP,

Please read our earlier reply to this question below, then let me know if any of that leaves further questions.

On 2023-10-26 by RRP

what is this on my ceiling? it is dry to the touch, could it be this thermal stuff or ghosting or?? plz help

On 2023-10-26 by Edits For Me La

what is this on my ceiling

On 2023-09-12 by InspectApedia-911 (mod) - soot stains may be from a safety issue such as a gas fired furnace, boiler or water heater that is not working properly

@EJ,

When you're seeing dirt or soot standing like that the first and highest priority concern is to be sure that there's not a safety issue such as a gas fired furnace, boiler or water heater that is not working properly.

The danger is the production of fatal carbon monoxide. So if you have gas fired equipment let's start by checking those. Also be sure you have working smoke detectors and carbon monoxide detectors in your home.

Once we've addressed those things We can start looking for other unusual suit or dust sources.

So let me know when you take those steps.

Peeling paint is a separate issue and could be related to bad paint, bad prep, or moisture.

On 2023-09-12 by EJ

Hello InspectApedia Team,

We hope you are doing well.

We are experiencing something that we have never experienced before.

A few months ago, we noticed a few spots / smudges on isolated walls of our living and dining room. They are easy to wipe off, but they keep resurfacing, which has caused us to investigate this reoccurring issue.

Please see the attached pictures.

All of the sheetrock in the house is brand new. Up close, it looks like the paint is peeling off the sheetrock. However, we are not sure what this is, and could use your help!

If you do not mind, when you have some free time, would you tell us what this issue is so we can get it fixed?

Thank you in advance. We look forward to hearing from you soon.

On 2023-09-09 by InspectApedia Publisher - investigate dark stains that look more random in shape, pattern, and location

@Ross,

The usual patterns of thermal tracking stains are diagnostic

I agree that those dark ceiling stains are worth some diagnosis, but they are not in the usual pattern in which thermal tracking stains appear.

Thermal tracking stains tend to occur at specific locations such as ceiling-wall juncture, or above heating baseboard, or at wall-floor juncture if there are air leaks from below

or

Thermal tracking will often map the location of wall studs or ceiling joists ("stripes" of cooler surface areas) or may show up as round spots that track the location of drywall nails or screws.

Your dark stains look more random in shape, pattern, and location.
I notice that they appear to be between two air registers - is that right? If so look for condensation leaks on or in the ductwork.

And if that rectangular lined area in the top of your 2nd photo is an access hatch to an attic air handler, that area certainly is worth a look.

If you can get access lift up insulation over the stained areas - if the attic side of ceiling drywall is spotless then we rule out a worry of leaks from above.

On 2023-09-08 by Ross

Hi, would someone be able to tell me what these marks are. They are diffuse brown patchy marks with a white line running through the centre. We have a MHVR system and air conditioning system with ceiling vents. Does this appear as thermal tracking or could it be a leak ?

...

On 2023-08-21 by InspectApedia Publisher - sooting stains indicate source of indoor soot or smoke

@Deb,

The uniformity of the sooting stains on that wall suggest that there has been a source of indoor soot or dirt or smoke or a similar source.

Speaking more precisely, because it does not seem to map the location of cooler wall spots like studs it's not ghosting in the more- technical way that we use it here to describe a specific pattern of or locations of such stains or deposits.

So it doesn't indicate insulation voids or poor insulation that often explains ghosting on exterior walls - in fact yours appears to be an interior wall - am I right?

Still the remedy is to clean and re-paint the surfaces.

On 2023-08-21 by Deb

Can someone please tell me if this is ghosting. I lived a the apartment for 4 years and when I pulled the furniture away it was on the carpet near the vents and walls.

On 2022-11-21 by InspectApedia (Editor)

@Gee,

Sorry but I don't know what that is. I've considered your comments and what you've ruled out.

On 2022-11-21 by Gee

I found this marks ( there's two identical one next to The other zoomed in on one for The photo) Behind the headboard. the room has been unused so it's not from resting Heads etc there are no pipes behind that wall Either thanks

On 2022-09-15 by InspectApedia-911 (mod)

@SK,

I think that's a leak stain.

Check above in the attic and let me know what you find.

On 2022-09-15 by SK

Is this a leak or thermal tracking? Tried look through the hole by removing the LED down lights couldn’t see any wet surface

On 2021-07-22 by danjoefriedman (mod) - seek outside help if landlord won't address mold concern

@Anonymous,

For rental units when there is a significant mold concern and the landlord is ducking the matter you need to ask for outside help.

See

RENTERS & TENANTS: MOLD ADVICE

HEALTH DEPARTMENT HELP for RENTERS

and also if you can stand it, read the other articles recommended at the bottom of those pages

On 2021-07-22 by Anonymous

This is my access panel in the hall that had water sprouting out that was closed up but not cleaned at all the maintenance man doesn’t even want to enter my unit because he does not know what it is a mold test was done however the property manager refuses to tell me the diagnosis.

On 2021-07-22 by danjoefriedman (mod) - need to investigate for possible hidden mold reservoirs

@T,

That sounds as if a professional investigation is warranted to trace the leak problem, the locations that got wet, and to define the scope of cleanup needed; There's a reasonable risk of a significant hidden mold reservoir.

On 2021-07-22 by T

@danjoefriedman, hi no it’s every where my fridge is just one that’s what’s growing inside it’s also on a lot my appliances that are in my cabinets my white dove deodorant stick is covered in it and that’s inside my medicine cabinet.

It’s also in the corner of the ceiling walls none of the water problems were handled correctly just caulked up I had a puddle in my bedroom that problem was never addressed just caulked the window seals to prevent more water coming in

I have an access panel above my shower and that leaks water whenever it wants my neighbors have also been complaining of mushrooms growing in their unit as well.

On 2021-07-22 by danjoefriedman (mod) - noticing this black stuff appearing on almost of my things

@T,

I can but guess that we are looking at an ice cube tray-

if it's left out of the fridge and was wet, it could indeed cause mold growth;

But if that's the ONLY mold growing anywhere in your apartment, then that's not the issue.

If there have been water leaks - and if water entered a ceiling, wall, or floor, and if those areas were not properly and sufficiently opened and cleaned, there could be a serious hidden mold reservoir in those areas;

Follow the water.

Also see HIDDEN MOLD, HOW TO FIND https://inspectapedia.com/mold/Find-Hidden-Mold.php

On 2021-07-22 by T

Hi I currently just moved into my apartment and have not been here for more than 2months and I am noticing this black stuff appearing on almost of my things I can feel it on things as well it feels dusty.

I have showed this to my apartment manager and it took her forever to send someone out now she’s telling me she doesn’t know if my results came back for the testing that was recorded at my apartment.

I also have a two year old and we both have asthma I literally been coughing everyday. I now can see it on my walls in the corners I suffered from 3 different water leaks already as well. Please help me

On 2021-06-26 by inspectapedia.com.moderator (mod) - check attic for leak source

@joseph novak,

It sounds to me as if you need a more thorough and more careful investigation. When you see stains following rain it's a little hard to convince yourself that there is no leak.

Try looking in the attic immediately above the stain and pulling back the insulation to look at the attic side of the ceiling plaster or drywall. If you confirm water stains there then look above that area at the roof.

On 2021-06-26 by joseph novak

3 yr old mfg. home. Before moving in, noticed a recurring wet spot/stain on bedroom ceiling. When a person came out, he found nothing wrong on the roof, and upon scrapping noticed the stain wasn't deep and plastered.

No problems since, until this morning (6/26/21), when upon waking saw two spots/stains, in the same area. Granted Michigan has and will have considerable rain in the next two weeks, but nothing in the past three years suggests it is not a roof leak.

On 2022-08-12 by InspectApedia-911 (mod)

@Gee,

Sure, glad to help.

The most likely explanation, cause, cure, for the pattern of stains you describe is given in our article series beginning above on this page.

This Q&A were posted originally at

InspectApedia.com HOME PAGE

On 2022-08-12 by Gee

I've noticed straight line streaks in my kitchen ceiling this morning (above this is bathroom). Cant figure out what's caused this, any suggestions to what this may be would be really appreciated.

Thanks G

Question:Thermal Tracking vs rectangular brown stains with light-colored stripes on interior walls in the UK

... ...

Thanks to your website, I now recognize some large black squares on a wall as thermal tracking. However, on the same wall where there were three large pieces of old furniture against wallpaper, there are rusty orange stains on the wall.

My home inspector did not know what to make of it, but he confirmed that the wall was dry. I suggested that perhaps it was tannin leeching, but I would very much like your thoughts before I spend $400 on mold inspection. Sorry that I don't have any better pictures. These are stills from a video I took.

[Click to enlarge any image]

I have attached three photos of each wall in the same room. Two walls are painted, and seem unaffected.

The wall with the wallpaper looks terrible in comparison. All three walls are also exterior walls. This room was added to the existing home around 1991. I also attached a fourth picture that shows one piece of wood furniture that is precisely where the first stain is.

There were two other pieces of wood furniture lined up next to the dresser, a small nightstand and an old rollback desk. I did not post these pictures publicly because I do not yet own this home, but I am happy to share publicly once I make settlement on the house if you think it would help other readers.

I get allergy induced asthma from mold, so I am worried, as this would be my bedroom. I greatly appreciate any direction or insight you could provide me with. - Anonymous by private email 2022/04/01

Moderator reply: test cut in wall to confirm moisture, leaks, mold? foxing stains on wallpaper?

It's common to find staining including moisture-related stains, mold, accumulated dust, or similar markings on walls in areas where there was less air movement or a cooler wall surface such as behind wall hangings or pictures or behind furniture that has been placed against an interior wall.

Often we find more-severe staining or dark black or brown areas particularly on the inside surface of exterior walls and occasionally as well on the surfaces of party walls or marriage walls in modular construction, doublewide mobile homes or other structures with a shared wall that may be open at its top, bottom, or both such that there are abnormal air currents inside the wall cavity.

Foxing stains on wallpaper?

It's possible that the brownish stains on the wallpaper are foxing stains, explained further

at FOXING STAINS on BOOKS & PAPERS

What I would do in that case is to go to the most stained area and make a small two inch by four-inch test cut through the drywall to inspect the wall cavity for signs of moisture. Also check the back of the piece that's cut out for mold. Let me know what you find.

At this website you will find articles on how to inspect test for and think about the risk of hidden mold - start with

HIDDEN MOLD, HOW TO FIND

TEST CUTS for MOLD in BUILDING CAVITIES

Watch out: if your home is an older one that might have antique green wallpaper that material contain arsenic. Don't panic, but do let us know the building age and location and estimated wallpaper age.

See ARSENIC HAZARDS at BUILDINGS

On 2021-03-10 - by (mod) - how to stop thermal tracking stains

@Doug,

To stop thermal tracking we

- find and fix air leaks in ceilings, walls, floor cavities

- add insulation where it's lacking

- find and fix abnormal soot sources such as heating systems, scented candles, pets, indoor dirt, cigarette smoking

- find and fix abnormal sources of indoor moisture or high humidity

Then clean the surfaces, seal with a lacquer primer sealer and then your finish paint
-

On 2021-03-10 by Doug

How can this be fixed, if painted over I'm afraid it will come back. Any thoughts??? I also have on exterior walls marks of the nail heads coming through. Is this lack of insulation?

On 2021-02-04 - by (mod) -

Thanks for the additional and helpful feedback. I didn't really suspect the cats. They didn't look perfumed.

About the electrostatic air cleaner it sounds entirely reasonable to me that charged particles are more likely to adhere to surfaces, in fact that's a technique that's often used deliberately in some situations.

All buildings have indoor dust and all buildings can suffer thermal tracking when there are temperature variations across the surfaces.

Of course when there's an extra source such as scented candles or a malfunctioning oil burner or a smoky fireplace or cigarette smokers, the rate of deposition is greater.

On 2021-02-04 by Anonymous

Thanks danjoefriedman for the feedback and confirmation! So glad it turned out not to be Chinese Drywall. We had even pulled some drywall to verify everything was looking normal behind the drywall. Those weren't the same candles by the way, the ones burned typically came in their own glass jars from scented candle vendors like Target or Lulu Candles on Amazon.

I have one more finding today, a big air purifier we use was deceptively sold as using "HEPASilent" filters. These aren't actually HEPA filters but instead use electrostatic charging to charge the dust to attract to the slimmer filter. From what I understand the dust not caught by the filter would then be prone to electrostatic clinging in similar fashion to walls and metal surfaces in the apartment

. I imagine this sort of charging of dust would simply magnify the amount of dust being trapped by Thermal Tracking? The model was "Blueair Blue Pure 211+ Air Purifier" from Amazon.

On 2021-02-03 by (mod) - thermal tracking and soot stains on ceilings, walls, electrical receptacles, and iMac computer

Incidentally, in this excerpt from one of your photos I notice those nice cat candles: are those among the soot-source culprits?

And your photo of thermal tracking at the openings of the rear support bracket of an iMac computer is an interesting example as well.

If there were actual overheating and burning of components inside the iMac would we add that this is an example of an additional source of carbon particles that comprise the sooty stain on that device.

From your electronics thermal tracking photos this example shows the effect of the combination of heat generated at a device plugged in to a wall receptacle and, perhaps, air leaks through the receptacle cover plate on the wall.

On 2021-02-03 - by (mod) - scented candles can make soot that contributes to thermal tracking

Yes, Mark, your photos show classic thermal tracking, and yes scented candles can explain such stains. Thank you for the photos and question and also for the nice comment.

Where we see soot tracking at electrical receptacles, at electronic devices, and also above heating baseboards and radiators it's the additional air current caused by heat from those devices that usually explains the black deposits. If you've got some nice examples of thermal tracking at electronic devices that'd be a nice addition.

No Chinese Drywall has nothing directly to do with the thermal tracking phenomenon. The offgassing from that drywall does not leave black stains.

Those details are at CHINESE DRYWALL HAZARDS

In several of your photos, an example is below, we can see not only the thermal tracking lines following wall studs, but the small dark round dots that mark drywall nails or screws.

On 2021-02-03 by Mark L

Hello, this site is an amazing and comprehensive resource in diagnosing an issue I'm having with my apartment, thank you! We have a strange issue with our walls and ceilings that we were afraid were symptoms of "Chinese Drywall" but the patterns very much match "Thermal Tracking" as documented on this page. To a degree that I am fairly confident that is what we are experiencing.

These are pictures documenting our issue, feel free to use them as examples if you can confirm that is what we are experiencing: https://www.dropbox.com/sh/99huyb8k9rjloi9/AADj0EsxGj3pPR60BPXLULy2a?dl=0

We are not yet certain where all the soot is coming from but the soot even follows electrical lines up wall outlets that are used heavily. I don't recall if I saw that mentioned on this page. Have you seen that as a symptom? There are related photos in my dropbox link along with examples of the same soot coming out of heavily used electronics like computers and projectors. My wife burns scented candles fairly regularly but I wonder if 7 years of candles 2-3 times a week could have such effects?

Thanks,
Mark - Oakland, California

On 2021-01-11 b (mod) - could solar panels cause thermal tracking stains?

David

How interesting. That our world sometimes has crazy stuff going on is plenty apparent from our current politics, but I can't blame rioters for thermal tracking, nor can I think of a simple way that adding solar panels on your roof would cause thermal tracking in a neighbour's ceiling.

I can list some very speculative causes: if the solar installation caused openings or closure of attic or roof cavity ventilation such that there was a change in air movement inside the roof cavity, that might be a factor in thermal tracking, but in that case it ought to appear on your ceilings, not the neighbour's.

Please invite your neighbour to read the article above and others in this series, or perhaps print a copy for her. Tell her I'll welcome her questions, comments, photos, and we'll be glad to see if we can be of further help.

On 2021-01-11 by David

My next door neighbour has reported thermal tracking stains in one of their upstairs rooms which joins to my house (semi-detached). She has suggested that the solar panels i put up on a part of my roof that pitches towards their house could be the cause of the issue

. I'm not sure exactly how they could be the cause and they were put up in the autumn of 2019 and are only now causing issues, but i'm wondering if you're aware of any mechanic by which external solar panels on an opposite roof could cause thermal tracking?

Many thanks for this information by the way, it's an excellent source.

On 2020-09-08 by Anonymous

Bathroom exhaust fan has condensation build up during periods of inactivity

On 2020-07-22 - by (mod) - find where the thermal tracking particles come-from

Kathleen

When we find ghosting stains in a building, in addition to cleaning and repainting as you describe, before proposing a "solution" we need to answer exactly the question you pose: where are the deposited particles (that make up the stain) coming from.

Our article series on ghosting stains list the common sources of house dust, soot, or other particles that comprise the stain, such as

- a malfunctioning heating system, gas or oil: watch out: this situation can be dangerous; gas heaters making soot are probably making potentially lethal carbon monoxide gas as well.

- a poorly drafted fireplace or woodstove

- smokers in the building

- pets, especially larger animals, in the building

- use of scented candles

- cooking

- outdoor soot particles in urban areas

and other such sources.

Sometimes we can point towards the ghosting source by noting where stains are worst.

Please see THERMAL TRACKING BRIDGING GHOSTING inspectapedia.com/interiors/Thermal_Tracking.php for a more-detailed discussion.

On 2020-07-22 - by (mod) -

RE-posting from FORENSIC INVESTIGATION of BUILDINGS inspectapedia.com/Building_Damage/Forensic-Investigation.php

Kathleen said:

How do I know if my ghosting is in a result of my new water heater and my oil boiler or it’s from a moisture in my home. I have a 3500 square-foot home and I can’t imagine it’s moisture. I painted my family room since the Covid and I washed an area of the wall and you can clearly see the difference. When I wipe my windows they are black.

Question: diagnose these dark wall stains?

I received a call from a couple that they have had stainings on their walls, black substance in their kitchen pantry, walls and on their plastic containers.
Please see attached pictures.

She claims that they painted walls less than a year ago and it came back. They have been living in the home for quite some time and started to notice the staining after the furnace (no baseboard) was upgraded to a newer energy efficient furnace in 2017.

They are using a newer filter which they claim were advised that it protects against allergies.

The home is well insulated, foam insulation in basement rim joist areas and excessive insulation in attic.

On your website I saw that you have a lot of talk about ghosting.

My client wants to know the best way to remedy the situation.

I have heard that cleaning the areas and re-painting with enamel painting will prevent it from recurring.

Even if that is the case how does one prevent the plastic containers and dishes from getting affected?

• Dov Ber Kahn, a home inspector in Rockland County, NY has contributed photographs of various building features. Mr. Kahn is a licensed home inspector in New York and New Jersey, and can be reached at Website: Kahnbhomeinspectors, Tel: 845-445-8234, Email: kdovber@googlemail.com

Moderator reply: classic thermal tracking sooting ghosting stains

The photos from your set in which I could see classic thermal tracking or ghosting stains on walls & ceilings are annotated here.

One photo shows what may be an air leak at a wall fitting, perhaps related to the central vac system - below.

I could not see the sooting or staining in some of your other photos but take your word for it. When there is widespread soot deposition it is critical to find the soot source, as I'll explain:

Watch out: aside from the classic causes of thermal tracking or ghosting discussed in this article series, particularly if people in the home don't have a "safe" dust and soot source (pests, smoking scented candles, fireplace use) then there is a risk of a very dangerous heating system safety problem; if a gas or oil fired heater is sooting badly there are risks of fatal carbon monoxide poisoning or an oil burner puffback explosion.

There is no sense in cleaning and sealing and re-painting before

1. The safety questions are addressed
2. The soot or dirt source is found and addressed

Then cleaning and painting and perhaps insulation and attic ventilation improvements are in order and are discussed in this article series.

You're welcome to print this article to give to your clients and to invite them to read more about the topic here.

On 2020-01-22 - by (mod) -

Sandy

Mold can be of just about any color; some species, in very light deposits might look like soot but usually there's more texture.

You don't normally see mold blowing out of a heating duct and onto nearby surfaces in a thermal tracking pattern such as shown on these pages but I can't say it's impossible.

When you see any sooty material coming out of a heating duct

- if it's oil fired you suspect the system is not running properly, has a leaky heat exchanger, is blowing soot through the building and is possibly unsafe too

- if it's gas fired heat, and the heater is producing soot, the system is very unsafe, risking fatal carbon monoxide poisoning, which is why I felt CO detectors are an urgent safety device to have properly installed and tested.

House dust blowing through HVAC ducts also makes dark gray or even black "sooty" deposits on surfaces and can simply be due to having run the system without proper air filters.

Perhaps hubby can post a photo - one per comment.

Watch out: If a gas heater or appliance is not working properly and is making soot that's unsafe, risking CO poisoning;

On 2020-01-22 by Sandy

So the Co2 checked out fine and I bought Co2 detectors for each room. The Hvac guy opened the unit and said there was black growth all over it . I did see the black but didn’t want to look to closely. He said we will need to replace the entire unit and all the ductwork. Would mold typically fly through the vent and deposit like soot?

And collect on windows and blinds? The house and unit are 8 years old. We had the house tested prior to moving in for mold and it checked out really well but it was ac season and not heating.

I’m pretty stressed. He said it wasn’t soot. And it was all black on the exchanger and the insulation . I could have my husband send pictures .,they are on his phone. I just ordered a dust test to check but wondered what you’ve seen.

On 2020-01-12 - by (mod) - definition of "wet" wood or drywall = 18%

If wood or drywall are around 18% the material is considered "wet"

On 2020-01-12 by Anonymous

Thank you so much! I will get some Co2 detectors and check on the furnace. Thanks again.,
Also , we had heavy rain last night and my inexpensive moisture meter had that wall reading 7.5 to 8.5 %. The room next to it was 6-7% but I’m sure there are different factors. The readings were very similar before and after the rain.

On 2020-01-12 - by (mod) - where did the thermal tracking particles or stains originate?

Don't rush to cut open the wall; if as it sounds, the stain you see is dust or soot it was deposited from the room side rather than having been caused by a leak or mold inside the wall.

The fact that the stains extend over broad wall areas and are not keyed to cooler areas such as marked by wall stud lines suggest that this isn't thermal tracking but that there is an indoor dust or soot source.

Clean it and have your heating system inspected for safety and for proper operation.

Watch out: If a gas heater or appliance is not working properly and is making soot that's unsafe, risking CO poisoning;

Be sure you have working carbon monoxide and smoke detectors properly located and tested.

On 2020-01-12 by Sandy b - do I need to cut open th wall

I moved a desk away from the wall today and noticed black blotchy build up in the wall. There was a vent near the wall and the vent was clear but the air flow was hindered.what should I do? I cleaned it. We have a gas stove and gas fireplace but it has glass cover that’s not been opened.

There was black build up on the windows when I cleaned. Do I cut open the wall? This photo is after my first go around to clean it.

On 2019-12-27 by Cathie

Thanks...I'll pass it along!

On 2019-12-27 2 - by (mod) - a cooler surface invites condensation of moisture onto that surface.

At least indoors I'd say the opposite: typically a cooler surface invites condensation of moisture onto that surface.

But yes you've got the right idea about the stain pattern. Differences in temperature explained by differences in wall materials (studs vs insulation and air space) mean different particle deposition rates.

Before cleaning the surface in a costly project I'd perhaps get up on a ladder and examine the material and try some simple cleaners: water, for example, or a mild soap solution. Beware of power-spraying that can blast water into the wall cavity - a real catastrophe.

Attic venting doesn't normally cause air current in walls but such odd conditions can occur if there are openings that permit attic air outlet currents to draw air up through a wall cavity; I've found that at holes cut for mechanicals and at gaps between marriage walls in modular construction.

If there is more attic outlet vent opening than air inlet openings at the eaves then the attic or roof space sucks air out of the building and increases heating and cooling costs.

On 2019-12-27 by Cathie

Thanks Dan...and happy holidays! Each of the units on the third floor that are showing this staining are occupied by elderly people, who may keep the thermostat cranked up, to say nothing of heat rising through the stories anyway. So, you are saying that where the surface is cooler (studs) there is no condensation, but where it might be warmer (between studs because of lack of insulation) dust from outside air might adhere to condensate

? I think we will attempt to have the window washers clean it as much as possible this spring.

Any suggestions for an exterior cleaning product or process? Do you know of a fix for this besides asking owners to turn down the thermostat? Could it have anything to do with inadequate attic ventilation? We already know that to be a problem in this building.

On 2019-12-27 - by (mod) - dark stains on exterior siding - Vancouver Island BC

dark stains on exterior siding - Vancouver Island BC

Cathie

I agree that your photo shows a type of exterior wall "ghosting" though the mechanism and staining particles are a bit different from those on walls and ceilings in the building interior.

I think that we are seeing an exterior wall that either lacks insulation or has air currents running in the wall cavity, causing a difference in temperature between the upper and lower wall surfaces.

Where we have a cooler surface and condensation of moisture onto the surface from exterior air, we expect to see greater adhesion of dust particles, thus causing the "staining". Of course there could be some other mechanism at work but that's my theory at this point.

See details at STAIN DIAGNOSIS on BUILDING EXTERIORS

and at INYL SIDING STAINS

On 2019-12-27 by Cathie

I have seen much reference to interior ghosting. What might be the cause or condition for black staining on third floor, all compass directions, exterior walls between studs? Photo [SHOWN ABOVE]

Vancouver Island, British Columbia, Canada...thanks!

Question: wall stains inside a foreclosed home

I hope you are well. We came across your very detailed webpage about thermal tracking and ghosting and think that is the cause of the black marks we see in a home we are purchasing.

The house is a foreclosed home (signed contract due today) and the walls appear to be consistent with ghosting. There are black streaks on walls, ceilings, and near vents. I have attached photos herein. The home has an oil burner. We have not been able to do an inspection and it appears the contract does not allow an inspection contingency.

One contractor indicated the markings are from a puffback of the oil burner, but now that the burner has been replaced, it may no longer be an issue. Another contractor said the markings might be from inadequate insulation in the walls. There does not appear to be mold. We are reasonably concerned with the possible health issues and future financial investment and are asking for your expert opinion.

Any help you can give would be greatly appreciated, and thank you for your help and assistance,

In either case, what are the potential problems that may come in the future? Is there a chance of mold growth in the insulation, or any other hazardous issues? Would you say these tracking marks is a red flag for the home? - Anonymous by private email 2019/09/17

Moderator reply: marks look like thermal tracking.

I agree that the marks look like thermal tracking.

I agree with your contractor - sort-of. I would not assert that there has been a puffback explosion without having inspected the heating system and its service history.
That could have happened in which case you'd find much more sooting on surfaces around the boiler itself.

Upstairs the same marks could be ordinary thermal tracking, perhaps marking where there are air leaks in the walls or ceilings or missing insulation. The fact that some of the marks are so very specific and some large rectangles argue for missing insulation in those areas.

Potential issues include energy cost for the home, mold, insect attack, other water or moisture or condensation damage; You need to inspect the attic above the stained area (or ceiling cavity and wall cavity if this is a first floor ceiling and there's finished living space above. It's trivial to cut into the worst area to inspect further before cleaning and re-painting.

Let me know what you find therein.

Looking further, the presence of those stains at the wall-ceiling abutment of an interior partition wall suggests that there may be air currents moving up some wall cavities and into ceiling cavities from below - combining with indoor moisture and dirt or soot sources to stain those specific areas.

Other stains map wall studs in the classic thermal tracking or ghosting pattern.

What are

the country and city of the home
the home's age
its insulation
its ventilation system (if any)

On 2015-04-08 - by (mod) - A home inspector ought to be able to help

Ghost

A home inspector ought to be able to help you think broadly about what's going on in the home. Look for the causes of ghosting that we list in this article series.

On 2015-03-31 by Ghosting in NYC

I seem to have ghosting on an interior wall of a bedroom that is adjacent to an exterior wall. I believe that the wall may be poorly insulated but I have no idea. What type of professional/expert do I need to hire to confirm that there is ghosting and to perform the necessary repairs? I am confused as to whether I should consult a home inspector, an engineer, a general contractor, some other expert, etc. Thanks!

On 2015-03-05 - by (mod) - how to fix thermal tracking ghosting stain problems

Dave

Since thermal tracking is basically house dust on cooler damper areas of a surface, the fix includes

- cleaning the existing surface

- re-painting if needed

- improving insulation

- reducing indoor humidity if it's excessive

- reducing sources of indoor soot and particles

Keeping the air moving may dry out surfaces - which is perhaps what "they" were thinking, but it'll also increase dust in air and air movement across surfaces, possibly increasing the staining.

Thermal tracking is normally an indoor phenomenon.

Outdoors - we're speculating. But

- I'd think you don't have much control over airborne dust sources

- running fans outdoors may increase air movement and dust movement over ceiling surfaces

- you don't have control over outdoor humidity

- you can make darn sure there are no leaks into your lanai/porch ceiling

and
- you can discuss with your paint dealer which coatings are least sticky

Use our contact link to send me some photos and perhaps we can comment further.

On 2015-03-05 by Dave

I have thermal tracking on a ceiling outside on my lanai/ porch how do I prevent this from happening. Builder sprayed bleach on mildew then applied Kilz and paint and it returns after a rain or heavy fog. They told me to run my fan 24/7 to keep air moving. Any thoughts?

On 2015-02-10 - by (mod) - Ghosting **might** be related to roof leaks

Ghosting **might** be related to roof leaks if high indoor moisture were causing extra condensation on cold areas of walls; I'd also look for leaks **into*** the wall cavities, making a test cut or two at the most suspect location.

But usually the root problems are not roofs but those we discuss above.

Finally: for life-safety you must get your gas heater checked for safe operation, including the heater and the chimney or venting system. **IF** a gas fired appliance were producing soot it'd be very dangerous, risking fatal carbon monoxide poisoning for building occupants. Don't sleep without working and properly installed CO detectors and smoke detectors.

Obviously I can't know what you have seen vs just have worried about but be safe.

On 2015-02-09 by Anonymous - serious ghosting problem in our home

My husband and I are having a serious ghosting problem in our home. In every room, on every wall and all the ceilings there are sooty lines where it appears to be the frame work underneath. When we purchased the house 4 years ago we were informed that a new roof was being laid down by the bank due to it being old.

We found out later on that the installers never put down paper before the shingles and now we are having minor leaks over our garage. Could the lines be from mold or our gas furnace? Who would we even ask to look at the problem?

I am experiencing ghosting in my home. I am having trouble finding someone to tell me why this is occurring. Who should I contact to diagnose the problem? I called three different mold removal places and they had never heard of it.

...

Continue reading at GHOSTING DARK STREAKS or LINES: CAUSES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see THERMAL TRACKING GHOSTING FAQs - diagnostic questions & answers about indoor stains traced to thermal tracking or bridging

Or see these

Recommended Articles

• AIR MOVEMENT in BUILDINGS - When, where, how & why air moves in buildings
• IAQ DIAGNOSIS via THERMAL TRACKING STAINS
• OIL BURNER SOOT & PUFFBACKS
• STAIN DIAGNOSIS on BUILDING INTERIORS - home
• THERMAL TRACKING BRIDGING GHOSTING - home
  • DEFINITION of THERMAL TRACKING
  • EIGHT INTERACTING FACTORS CAUSE GHOSTING
  • AIR VELOCITY & MOVEMENT PATTERNS
  • COMPOSITION of DARK GHOSTING STAIN PARTICLES
  • GHOSTING STAIN INSPECTION
  • GHOSTING DARK STREAKS or LINES: CAUSES
  • GHOSTING DARK RECTANGULAR STAINS: CAUSES
  • GHOSTING DARK STAINS from AIR LEAKS
  • GHOSTING DARK STAINS on INSULATION, AIR BYPASS LEAKS
  • GHOSTING STAINS on WALLS
  • STAINS CANDLES FIREPLACE WOODSTOVE
  • STAINS DIAGNOSE IAQ PROBLEMS
  • STAINS INDICATE SAFETY CONCERNS
  • STAINS MISTAKEN for GHOSTING
  • THERMAL TRACKING REMEDIES

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THERMAL TRACKING BRIDGING GHOSTING at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

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