This article describes & diagnoses heating equipment as the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, thermal bridging stains, building air leaks, and building insulation defects.

Often these stains are mistaken for toxic indoor mold. 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.

Q&A on Ceiling / Wall Stains From Heating or A/C Systems

These questions & answers about indoor stains on ceilings and walls that are traced to heating or air conditioning systems or their ductwork were posted originally at STAINS HVAC SOOT or DUST - so please be sure to also review that article.

[Click to enlarge any image]

On 2018-09-30 by (mod) - dust and debris deposited at ceiling registers

duct air leaks

It looks as if someone covered an air supply register to cut down on supply of warm or cool air in the room where your photo was taken - but the cover is not perfectly air tight.

Air movement from any cause, heating or cooling ductwork or even simple air leaks into or out of a building space will deposit dust at openings.

On 2018-09-30 by Tina

Air Leak?...

On 2018-09-29 by (mod) - what are those black marks?

Tina

Most likely, house dust, from an air leak.

Air blowing out of a ceiling register will often deposit house dust on nearby surfaces in a pattern that corresponds to the direction of air movement from a heating or air conditioning system.

Watch out: if the heating system that's supplying this air is not working properly and is actually producing soot then the system is unreliable and un-safe and needs service promptly.

On 2018-09-29 by Tina

Could you tell me what black marks are please..

 

On 2018-09-22 by (mod) -

Jennifer I'd like to help but I can't see anything in the photo; A clue may be to look more closely where the dust is most-concentrated

On 2018-09-21 by Jennifer

I bought a brand new home and in my upstairs master and only one one wall it is covered in a orange dusting and it’s even on my trim and around the socket

On 2018-03-29 by Laura

I have vacuumed the wall only to find a thin fine black dust and I get it off the floors and carpet too. I have not been feeling so good since I have moved in here.

On 2017-04-28 by (mod) -

Basically you look at and correct:

1. missing insulation
2. high indoor humidity
3. sources of unusual dust or soot such as scented candles or a poorly-functioning (and unsafe) heating appliance

On 2017-04-28 by kathryn

what and how do i treat this problem, as i have to decorate every 6 months

On 2016-10-28 by (mod) -

Marie, I'm unclear which "firebox" was inspected as well as unclear why the HVAC tech focused on CO testing. If your heating system uses gas fuel, of course, testing for CO is an extra safety step but higher priority is having working CO and smoke detectors properly located in the home. CO tests are unreliable as a simple change in building conditions can convert from no detected CO to dangerously high levels of CO later. All we know is that CO was not detected - at the time of the test.

About the ghosting problem, you've addressed cleaning, repainting, and perhaps some of the soot or dust particle sources. However even without a focused soot source such as a fireplace or defective heating system, normal house dust, increased in level by carpeting, pets, and some other activities, can produce enough particles to show up as ghosting.

Searching InspectApedia using the search box just above or in the ARTICLE INDEX find THERMAL TRACKING BRIDGING GHOSTING the home page for this topic, on which we've also researched and written quite a bit.

In that article series, of whichSTAINS HVAC SOOT or DUST is one, argues that in addition to dust particle sources, ghosting or thermal tracking shows up in buildings with

- poor or incomplete insulation

- high interior moisture levels

- air circulation patterns moving dust across cooler surfaces

The open windows in your home improve fireplace draft (though an outside air source dedicated to the fireplace and an enclosed fireplace with glass doors would be more efficient) but they also increase air movement and updrafting.

As you haven't posed a specific question I offer the above to help out; after reading our article series don't hesitate to ask if that material seems unclear, incomplete, or leaves you with more questions. Working together will make us smarter.

Daniel

On 2016-10-28 by Marie

I have done extensive search and read on the internet in regards to soot, ghosting on walls, etc. We bought our house a year ago, had black sooting stains above heat registers and ceilings and thermal tracking upstairs on walls and ceiling. I spent a whole year washing the walls and ceiling with ECO-tps, then bought a good quality primer and paints (Ben Moore), and painted the whole house.

We changed the natural gas fireplace (direct vent) and furnace (all brand new)this past couple of months. The room where the fireplace is located has black fine particles (like soot)on TV, computer screen, table, armoire,walls everything, even when I vaccuum.

The fireplace still emits an unpleasant odour (it has been used now about 80 hours since new).

The HVAC techn came , tested for carbon monoxyde (0 reading), looked inside the firebox, said everything is fine. There is black fine particles on top of the box, he said that is paint residue from manufacturing, flaking off. I am really perplexed and upset, wondering what's going on.

The house was built in 1977, it is air tight. There is no humidity problems in the house. We do not have an air exchanger. We always open a window near where the fireplace is, and also one upstairs.

On 2016-09-24 by (mod) -

First try sending me images - see the page bottom CONTACT link.

On 2016-09-24 by sheryl

We were wondering if we posted a pic of our ac ducts & stains on our ceiling would or could you be able to take a look & give us your opinion.

It is in a yr old RV & no one smokes or ever has. We both are having some health issues , me more than my spouse & we are not happy with the stains on ceiling & the soot looking stuff on the ceiling near the AC register. Also our 2x4's are showing through the wall paper as if to be a shadow which it isn't. Any help would be appreciated. Thank you. Enjoyed all the info on your site.

...

Continue reading at STAINS HVAC SOOT or DUST - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• STAINS at HVAC REGISTERS
• STAINS on INDOOR SURFACES, PHOTO GUIDE
• THERMAL TRACKING BRIDGING GHOSTING

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