Questions & answers about Indoor stains in buildings traced to black or dark thermal tracking or ghosting lines:

Thermal tracking FAQs, diagnostic questions & answers about the pattern, location, & causes of indoor stains explained by thermal tracking, ghosting, or bridging.

This article series 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.

Questions & Answers (FAQs) about Thermal Tracking, Ghosting, Sooting, Thermophoresis, Electrostatic Deposition, Plating-Out Stains

These replies to reader questions about Bridging, Thermal Tracking, Ghosting, Sooting, Thermophoresis, Electrostatic Deposition, Plating-Out Stains were posted originally at THERMAL TRACKING BRIDGING GHOSTING - home (or its companion articles) - please be sure to reviewe the causes, effects, and cures of ghosting stains starting at that page.

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Question: round circular ghosting worries home buyer

2016/08/19 concerned buyer said:

Hi, can ghosting also be just small circles instead of lines? I seem to have the same problem you describe in my bathroom, which is poorly ventilated and on an exterior wall, but the black spots are

(1) above the circular bulbs over my vanity and

(2) dots at regular intervals about 12 inches apart (not on internal walls);

(3) gray in no real pattern in the corners.

[Click to enlarge any image]

We just bought the house a few weeks ago...so we are really hoping it is not indicative of a mold problem. I can send a picture or several if that would be helpful. We live in the desert, so it's usually pretty hot and dry.

2016/08/20 concerned buyer continued by private email

I had just commented as "concerned buyer" on the page about ghosting. I'm attaching some pictures from my bathroom. I hope you can see the dots. I'm also noticing that there are a few on the ceiling as well. I hope these are visible in the pictures. Again, the areas I'm noticing are

(1) above the lights over the vanity,

(2) in the corners, grayish in no pattern, and

(3) on the upper parts of the walls (and a bit on the ceilings) regularly spaced dots. You have my permission to post these on the page if you would like, although I would ask that you not use my real name.

I don't mind looking at them and maybe eventually painting over them, but I want to make sure it is not dangerous (like mold).

We live in the desert so it is generally hot and dry, but this house has had some problems with plumbing in the past (apparently resulting in damage to the ceiling in the kitchen, below this bathroom, and also to the wall behind the shower in this bathroom - not while we were living here, and I believe that the issues were fixed promptly).

I am deathly afraid that there is going to be tons of mold behind the walls and that's it coming through or something. (The prior owners were an older couple and treated the house very well, so I don't think this would be the case, but still, you hear some scary stories).

You can also see in some of the pictures that there is what I am fairly certain is actual mold growing on top of the shower stall. My hope is that I can spray that with some Tilex and kill that off, and that again, it's just on top and not behind the stall in the walls.

The house was well cared for over the years so I am somewhat hopeful.

Any thoughts you might have would be very welcome!! Your site was a great help to me last night when I was trying to figure out what was going on, so thanks for providing a really useful resource.

Reply:

Concerned:

Great question. Absolutely, yes. For example we sometimes see black spots on drywall-covered walls or ceilings. Those mark the location of drywall nails or screws that are a bit cooler than the surrounding material, thus inviting early dust deposition or ghosting.

You can use our page top or bottom CONTACT link to send photos for comment.

About your photos, two of them give such very clear examples of thermal tracking that I include them in this discussion.

The photographs illustrate thermal tracking or dust deposition. While nobody can declare a home "mold free" by an electro-email-inspection of your photographs, it is not at all likely that any of the stains in your photos are mold growth. We can track the black spots to regular building features:

1. Round black spots on a ceiling close to and above equally-spaced light bulbs in a bath light fixture suggests dust deposition in areas of increased air movement: convection currents over the warmer light bulbs means more air movement upwards to the ceiling over each bulb.
2. Gray areas in the corners of ceiling/wall intersections suggest cooler surfaces, higher surface moisture in those areas of less air circulation and so as air does ultimately move across those surfaces it's is likely to cause the staining there.
3. Cooler surface on walls at drywall nails or screws means higher moisture there and so more dust deposition than on the surrounding warmer more dry surfaces; the spacing reflects the spacing of the drywall fasteners that in turn reflects the probable location of framing members.

At MOLD APPEARANCE - WHAT MOLD LOOKS LIKE you will see that while mold growth indoors on building surfaces sometimes occurs in spots or other semi-regular patterns, only in rare instances will the mold growth track actual building features like light bulbs and drywall nails. And a closer look at mold growth on any surface easily distinguishes it from dust deposition.

Take a look at the photos in that article and do let me know if questions remain. - Mod.

 

Question: black deposits appearing evenly on vertical surfaces

(Jan 17, 2012) John Dabbs said:

A friend has black deposits appearing evenly on vertical surfaces at the top of an internal lounge wall, just under the coving. The wall-hung pictures also have severe dirt 'shadows'.

The appearance is similar to that I experienced when I had a de-ioniser in use in my bedroom, but there is none in the friend's lounge but there is a tv and modern wall-hung logfire-effect unit.

Heating is by conventional hotwater radiators. The house is right on the sea front (at Bude) and fully exposed to off-sea winds.

Could the cause be thermopherosis? Caused by deionisation from sea spray? Or what? And what might the solution be? No nearby pollution source that I can identify.

Reply:

John, if by "appearing evenly" you mean at even spaces or intervals such as marking the intervals of building framing members, that would be a classic diagnostic clue indicating thermal tracking.

And yes, using a "de-ioniser" (more likely it was an ionizer - a device that puts an electrical charge on dust particles, causing them to plate out on wall and other building surfaces) can contribute to soot and thermal dust tracking stains on building walls and ceilings.

I'm not sure of the role that off-sea winds would play in thermal tracking - it depends ... for example on the effect of winds on building heat loss. Sea spray itself sounds an unlikely cause to me as I don't imagine much sea spray enters the building interior.

Even common house dust will be enough of a particle source to explain thermal tracking in buildings, but where there are additional dust or particle sources the effects will appear more rapidly and at more extreme levels. Examples include an oil burner that is not working properly, producing soot; use of candles, scented candles, woodstoves, fireplaces, or even burning cooking materials.

Pets can also be contributors to such indoor stains.

The solution to thermal tracking includes:

- identify and remove sources of high levels interior dust or particulate debris as much as possible

- identify locations of building air leaks and heat losses and correct them

- add insulation, particularly where there are voids

- monitor and correct high levels of interior moisture

Reader follow-up:

Many thanks indeed, for your comments. Perhaps I should have said that the staining is "uniformly" spread ie a consistent level along the upper perimeter of the room, graduating in intensity as the ceiling is approached. The wall construction is, I believe, solid masonry (I'll check that), and the effect is apparent on all walls whether internal or not.

One wall - facing the sea - has a large double-glazed sliding patio door and a "soot" film appears on this after only a few days after cleaning.

Yes, I should have referred to an ioniser - I apologise! It was because of the similarity of this problem to my previous experience with one of these that I was wondering if this was due to an ionising effect somehow. Hence I was wondering if excessive sea spray could cause ionisation? Clutching at straws?

The household has a cat, but it's a large, open house. The room is clean with few furniture pieces, all modern, with a fitted carpet. There are a few nearby properties, all as far as I know with natural gas heating.

Completely residential area, and I can't identify an probable sources of dirt/soot particles, but I'll have another look around. No woodfires, candles or oil burners.

Two of the walls have hot water radiators fixed to them, but the staining is at the same level on a third wall with no heating fixed to it.
Any further thoughts?

Question: How do I clean painted wall from streaking

(Feb 26, 2012) Jerry said:

How do I clean painted wall from streaking

Reply: 6 steps to Fix Ghosting Stains

Jerry, identify the cause, fix that source first; then wash and seal and paint the walls. You might want to use a lacquer primer sealer for best results.

See

6 steps to Fix Ghosting Stains

at THERMAL TRACKING GHOSTING FAQs-3

Question: possible ghosting from a defective gas stove

Apr 7, 2012) sue white said:

we have a friend with a house that has ghosting at the 2nd floor ceiling and top 1-2' of wall where it meets the ceiling; the nails are also popping at this ceiling/wall juncture.

the house is entirely electric with exception of a gas fired stove in the lower level of the split level home.

do you think the ghosting is due to a malfunction with the stove or some other issue? thank you

Reply:

Not likely - but

Watch out: a gas cook stove that is making visible soot is not working properly and is unsafe, risking fatal carbon monoxide poisoning.

Question: how do I get rid of thermal tracking?

(Feb 20, 2014) Anonymous said:

how does one get ride of thermal tracking.

Reply:

Good question, Anon.

First, the actual black sooty marks can be removed by cleaning washable surfaces; typically we use a non-sudsing detergent. On carpets the carpet would have to be shampooed.

But to complete the "get rid of thermal tracking" process we need to look at what is causing the soot or dust marking and address the underlying causes (which are discussed in this article series).
As some examples:

- look for and fix any extra sources of dust or soot like a poorly-tuned oil burner, use of a fireplace, scented candles, smoking

- check the indoor humidity level and if it's too high we need to fix moisture sources or dehumidify the building - see HUMIDITY LEVEL TARGETS

- See THERMAL TRACKING REMEDIES for complete details

Question:

(Feb 24, 2014) Sarah said:

My husband and I just notified a stain on the ceiling that wasn't there 7 months ago when we moved in.

It's a light pinkish tan stain on a textured ceiling. It is about 3 ft shy of an air vent in our breakfast nook. It does look like a type of moisture stain but nothing similar to your mold patterns you've posted pictures of on the website. This is a ceiling below our guest bath. Any ideas?

Reply:

Sarah, I'd have to see some sharp photos (you can use our CONTACT link if you like);

Generally the location and size of a ceiling stain will suggest something about possible sources, e.g. a possible leak from above.

Question: dark marks forming on our ceilings in winter

4/2/14 Kathy said:

we have been experiencing the same we moved to a house 2 yrs ago and especially during the winter it seems to get darker marks. this winter we noticed it a lot more.

I have pictures but unsure how to load them here. we see the ceiling marks by the beams as well as the corner marks or above the heat. should we be concerned?

Reply:

You can use the CONTACT link at page bottom to send us photos. I'll take a look.

Question: thermal tracking stains on carpet in the middle of a room?

(Oct 7, 2014) Brennan said:

Have you ever seen this in carpet in the middle of a room (not near the baseboards). I received a moisture meter to check some ceiling stains to see if they were active or inactive after the former owner replaced the roof. I was using the moisture meter to check the basement- all surfaces.

I found some areas in the basement carpet where the moisture meter was high but dry to the touch. I run a humidifier in that room and it doesn't work very hard to maintain 45-50 rh%

It has a 'line' type stain. A bit darkened (carpet is grey, so this is darkish grey), but not like the other areas where there is actual infiltration soiling (I have seen it is one room near the baseboards but is completely dry). My home is old, so of course it has air leaks.

The former owners had a couch over this area, so I thought it was due to that. Adjacent staining is yellow coloring and also shows moisture in the meter. So moisture and a line/ghosting in carpet. The carpet is gross anyway, so I thought about peeling it back to see if there is a crack in the slab (60+ yr old house).

A contractor friend, without seeing it, said it was radon gas escaping. That seemed like a stretch, since Radon is colorless. I think though, perhaps he meant, air is feeding through the crack and depositing soil on the carpet.

If I do find a crack- should is seal it with concrete/caulk and re-carpet and be vigilant about dehumidification?

Reply:

Brennan

A couple of points to consider:

Most moisture meters, if we exclude thermal imaging, rely on measuring differences in electrical resistance to detect moisture. But other contaminants or materials can also decrease resistance in an area of building material. So not every reading variation is necessarily truly detecting moisture.

Some attention, particularly looking for possible moisture sources, are key.

Both pin type moisture meters (Delmhorst for example) and electronic moisture meters (such as some Tramex meters) can be fooled by metal nearby: pipes, foil faced insulation, wiring.

Second: no moisture meter, nor thermal imaging device, can detect old leaks that have since dried, even though the leak might have initiated a building problem with rot, insect damage, or mold contamination. This is why we argue that reliance on meters and imaging alone for water or mold detection are unreliable. But the instruments are indeed useful, in thoghtful hands. And neat too.

See inspectapedia.com/home_inspection/Thermography_Info.php

(Oct 9, 2014) Brennan said:
Thanks for your comment.

One thought (using my science background) was that the moisture meter gives a high reading on what looks like an old dog urine stain (former owner had dog). I had the thought that these left over salts and ions from the urine might act as a weak conductor and activate the moisture meter.

On the internet, it seems that carpet companies use moisture meters to find hidden pet stains, because the salt from the urine can draw moisture from the air (or even just the natural evaporation of the concrete slab). So, thanks for your help. I tend to over-think things. I agree, it is a neat tool.

(Oct 9, 2014) (mod) said:
Interesting Brennan, and thoughtful. I agree with the salts / ions theory for both of the reasons you offer.

It's not over-thinking. The more we understand the better we can find and fix or prevent aggravations. Thanks. x

Question: is it medically harmful to live in a building where there is thermal tracking?

(Apr 27, 2015) is it harmfull to have lived in a dwelling where this condition exist said:
is it harmful medica

lly to have lived where thermal tracking exist

Reply: maybe

Harmful:

The black stains on walls or ceilings are not themselves likely to be harmful to you - when we are discussing thermal tracking - but the conditions that cause the appearance of these stains range from harmless (indoor house dust deposited on cooler more damp areas where there is less insulation or more heat loss) to extremely dangerous (oil burner soot from a misfunctioning oil burner that risks a puffback explosion).

So it's the cause of the stains that's important to understand.

Question: other thermal tracking patterns: spots lined up in rows

(Jan 3, 2016) Jason said:
Instead of dark streaks, I see spots that line up in straight patterns. Are they thermal tracking?

Reply:

Good question, Jason.

Most likely, yes, you are seeing thermal tracking or ghosting showing up where the drywall nails or screws secure the drywall to the building framing.

I'll bet that in addition to the spots lining up in straight patterns, if the home is a relatively modern one the lines are 18" or 24 apart and are parallel, marking the locations of wall studs or ceiling joists.

Please use the page bottom CONTACT link to send me some sharp photos of these spot lines and I can comment further.

Question: walls started to darken and soot collected shortly after I moved in

(Mar 22, 2016) Jeanelle said:

Hello, I moved into an apartment this past December and I noticed shortly after moving in I noticed the walls starting to darken and things that were plastic collecting a dark soot on them along with the windows, my area rug carpet has a ring around the edges along with the back of the front door that is metal has black smudges all over.

I also open cabinets and you can see rings around where items are set. It's an older apartment complex built in the 80's I had the apartment manager come in and first thing she said it was my 1 candle I light.

I used the same candles in my last home where I lived for 7 years never experienced that and that home was built in 2007.

I have since stopped using any candles and the problem continues I don't feel this is good and what can I have them do to figure this out!!!! Please help thank you..

Reply:

Candles can produce more soot than you'd think, Jeanelle, especially scented candles. Or there could be another soot source in the building. If soot is coming from the heating system the system could be unsafe.

If the problem were use of candles I'd expect to see soot tracking strongest in the room where the candle(s) is (are) in use. If you see equally sooty tracking marks in other rooms there is another dust or soot source.

The problem could be other airborne particulates or contaminants depending on where you live and what activities are nearby - more than I can guess from an e-text.

I'd start by cleaning a sooty surface and watching what happens, and I'd also be sure that someone has inspected the heating system for safe proper operation.

Particularly, soot from an oil burner risks a dangerous puffback explosion; soot from a gas burner risks fatal carbon monoxide poisoning.

You can provide a first line of protection for yourself (an other apartment occupants) by proper installation of smoke and carbon monoxide detectors. If you have them, be sure they're properly located and working.

Question: thermal tracking on the exterior of large commercial buildings

2016/03/30 Chris said:

Thank you for the information I found this article very helpful. I have a client that has what appeared to be thermal tracking on the exterior of large commercial buildings. It appeared about one year after repainting. It looks like it was manifesting near the metal supports every 16 feet or so (perfectly straight lines top to bottom on the walls).

It is possible to get thermal tracking on the exterior of a building or am I looking at something else entirely?
flag like

Reply:

Chris:

We might see other types of stains mapped on the exterior of a building but strictly speaking it I wouldn't call these the thermal tracking phenomenon I discuss in the article above - that's an indoor condition.

Still I wouldn't rule out regular deposition of outdoor airborne soot or diesel particles or other dark particles on a building exterior that might be related to variations in building wall moisture, temperature, stickiness, or other features.

It would be diagnostic to look at all sides of the building as well as to know more about its construction, history, leak history, occupancy, use, proximitity to significant airborne soot or debris sources, etc.

Some additional investigation is in order; I agree with the direction of your thoughts, such as noticing the regularity of interval of appearance of a stain and its shape and size - those are helpful clues. Let's see what else is at that location and what's going on.

You could be seeing evidence of air leaks, condensation, variations in coating application or something else.

Use our page-bottom CONTACT link to send me photos if you like and I may be able to comment further.

Question:

(Mar 30, 2016) Chris said:

Thank you for the information I found this article very helpful. I have a client that has what appeared to be thermal tracking on the exterior of large commercial buildings.

It appeared about one year after repainting. It looks like it was manifesting near the metal supports every 16 feet or so (perfectly straight lines top to bottom on the walls).

It is possible to get thermal tracking on the exterior of a building or am I looking at something else entirely?

Reply:

We might see other types of stains mapped on the exterior of a building but strictly speaking it I wouldn't call these the thermal tracking phenomenon I discuss in the article above - that's an indoor condition.

Still I wouldn't rule out regular deposition of outdoor airborne soot or diesel particles or other dark particles on a building exterior that might be related to variations in building wall moisture, temperature, stickiness, or other features. It would be diagnostic to look at all sides of the building as well as to know more about its construction, history, leak history, occupancy, use, proximitity to significant airborne soot or debris sources, etc.

Some additional investigation is in order; I agree with the direction of your thoughts, such as noticing the regularity of interval of appearance of a stain and its shape and size - those are helpful clues. Let's see what else is at that location and what's going on.

You could be seeing evidence of air leaks, condensation, variations in coating application or something else.

Use our page-bottom CONTACT link to send me photos if you like and I may be able to comment further.

(Mar 30, 2016) Chris said:

Thank you for the quick response. Unfortunately the building was repainted (again) so I don't have any photos but the phenomenon has puzzled me so I thought I would search the net incase it was a common issue. I appreciate your feedback and if it happens again I'll be sure to get photos.

...

Continue reading at THERMAL TRACKING BRIDGING GHOSTING - home or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see THERMAL TRACKING GHOSTING FAQs-2 - more-recent questions & answers about thermphoresis, ghosting, thermal tracking stains, causes, cures.

Or see these

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