Indoor air quality or unsafe heating systems may be indicated by ceiling or wall stains or ghosting lines:

If the stains in your building are caused by deposits of airborne soot from an oil or gas fired heating system, that system is dangerously unsafe, as this article explains. Fireplaces with poor draft may also result in indoor wall & ceiling stains both uniform near the fireplace or as lines or spots shown at the page top photo.

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.

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

What Can we Learn about IAQ Problems From the Pattern of Indoor Surface Stains?

Since thermal tracking, or soot marking, or "thermal bridging" always tell us about missing or openings in building insulation or about air leaks, we can learn other facts about a building such as those listed here:

[Click to enlarge any image]

Our photo of soot stains around a fireplace indicate high indoor soot levels, an indoor air quality concern that can also point to a poorly-operating fireplace.

• Identify unsafe heating equipment or poorly-functioning fireplaces:
  
  Use thermal tracking marks on interior building walls and ceilings, particularly where they vary from room to room, to diagnose poorly-vented chimneys such as fireplaces that do not work well (also look for soot stains at the hearth face).
  
  Watch out: Such ghosting streaks or spots may also indicate poor and even unsafe operation of central heating systems since a poorly maintained oil burner will often leak soot into a building interior, and a dangerously un-vented gas appliance may also produce both soot and potentially fatal carbon monoxide gas.

• Indications of leaks, moisture, risk of hidden mold or other contaminants:
  
  The gross mold contamination shown in our photo doesn't need an expert to recognize that there is a dangerous mold contamination issue in this building.
  
  But more subtle true thermal tracking or ghosting stains shown in additional photos in this article series can point to possible but otherwise hard to spot building defects:
  
  Moisture accumulation as condensation in building cavities
  
  Air leaks into ceilings and walls
  
  Actual water leaks hidden in building cavities - roof leaks, plumbing leaks,
  
  or below ground level, ground water or roof spillage leaks into the building that are causing moist indoor conditions exacerbating thermal ghosting staining.

More Indoor Stains Identified as Ghosting or Bridging: stripes on ceilings or walls

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.

Safety Warnings about Black Stains Indoors: Unsafe Heating Equipment

Watch Out: Ghosting or thermal tracking stains are usually house-dust or soot deposition on walls, ceilings, and perhaps floors.

But if that dust or soot are coming from an abnormal source such as gas-fired heating equipment (or in some cases oil fired heating equipment) the equipment could be unsafe:

the same conditions that produce indoor soot from an oil or gas fired appliance can be producing dangerous, potentially fatal carbon monoxide gas.

Oil fired heating equipment does not produce carbon monoxide gas as easily as an improperly functioning gas fired system, and conventional oil fired equipment often runs (normally) producing a little internal soot or "smoke".

But if your oil heating equipment is producing visible soot indoors or if it's making strange and horrible noises, it's probably not working properly, and it too could be unsafe, risking a "puffback" explosion that can blow soot throughout a building and in severe cases can risk a fire.

A gas fired heater normally burns quite clean, but if there is a combustion air problem or a flue gas venting problem the gas fired equipment can very quickly shift to producing soot and / or dangerous carbon monoxide gas (CO).

If you see soot coming out of a gas fired heater you should turn it off and call an expert service technician right away.

See CHIMNEY INSPECTION CHECKLIST and

see COMBUSTION AIR for TIGHT BUILDINGS.

Make sure that your home has working carbon monoxide detectors and smoke detectors installed in the proper locations before moving on to less urgent concerns with indoor stains or thermal tracking.

Harmful indoor mold may also appear as regular stains indoors

Usually indoor mold growth patterns depend on the wetting-pattern of building surfaces and modl growth tends to be rather uniform across its area of contamination. But I have found mold growth on a wall stopping at a rather regular horizontal or vertical line that mapped exactly the joint in drywall.

A common cause of such regularity in mold growth patterns is mold growth up wet drywall from flooding or from a wet floor; water and dampness originating at floor level rise in the wall but may be interrupted by a drywall joint.

In the photo above you see severe black mold growth on lower drywall along the wall, stopping as water stopped at a drywall joint.

See MOLD APPEARANCE - WHAT MOLD LOOKS LIKE for details.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: thermal tracking on garage ceiling caused by car exhaust?

(Oct 2, 2014) Sam said:
Wow, what a great resource, thank you so much for all the info!

Question: Garage ceiling has this tracking at all the drywall seams. I can see that the ceiling was insulated.

Dark spots exactly correspond with the 12" joint compound finishing knife. Could it be that the compound was simply not sealed properly when it was painted? Also, could exhaust from cars cause this-it's nowhere else in the house.

Thanks, I love this site!

Reply:

Sam

I don't think so. More likely the joints are over studs, pipes, or cooler surfaces that pick up a bit more moisture and thus particle deposits thus stains.

Yes car exhaust could be a particle source, also a moisture source. And if the car is burning oil and is left running for some time in the garage these effects would be increased.

Watch out: for potentially fatal carbon monoxide hazards if car exhaust can enter the home or accumulate in the garage.

Question:

(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.

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, Dan, 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:

(Feb 26, 2012) Jerry said:

How do I clean painted wall from streaking

Reply:

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.

Question:

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.

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Continue reading at IAQ DIAGNOSIS via THERMAL TRACKING STAINS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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• OIL BURNER SOOT & PUFFBACKS
• STAIN DIAGNOSIS on BUILDING INTERIORS - home
• STAINS DIAGNOSE IAQ PROBLEMS
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