Frequently asked questions or FAQs about distinguishing mold contamination from other building stains, debris, or particles.

FAQs help recognize non-fungal (not mold) stains, particles, debris in or on buildings. This article series describes indoor stains and deposits that are not building mold or in other examples, harmless cosmetic 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 - save your money.

Stains in Buildings: FAQS on scary-looking, usually harmless indoor stuff that is sometimes mistaken for mold

On 2020-10-28 by (mod) - how to remove spider and fly droppings and spots

Jacob:

Insect spots, particularly spider droppings but also from flies, can harden and thus difficult to remove.

I've had good luck by wetting the area with a spray glass cleaner such as Windex®, letting it soak for a few minutes to soften the material, then wiping it off with a clean dry paper towel.

Try your spray first on an unobtrusive location so that you can be sure the spray won't cause its own discoloring. Spray a bit, wipe gently, let it dry.

On 2020-10-28 by Jacob Young

Tried to scrub fly @#(! off my ceiling and later found that it's left a shadowy mark on the ceiling, I've tried sugar soap to get it off but with no luck. Any thoughts as to what I've done? Standing under the marks you can't tell they're there but from a distance with the sunlight coming in they standout like anything.

On 2020-10-16 by (mod)

That looks a bit like mold growing on a p;aitned surface - more-likely if the sealer is not itself mold-resistant.

On 2020-10-16 by Nancy

Hello,
These spots are all along the bottom only of a cement wall in my basement. This wall is not an outside wall. There are a smaller number of the spots on part of another wall, bottom only, that is an outside wall.

Could it be mold or the remnants of a sealer that may have been applied to the bottom of the wall? It has been there a long time and to my knowledge has never changed.
thank you.

On 2020-09-14 by (mod) - track down soot sources

Katherine:

Watch out: when tracking down soot sources, start with having your building heating equipment, gas or oil fired equipment inspected for safety.

Soot, especially from gas fired equipment, is a warning of improper combustion and risks fatal carbon monoxide poisoning.

Be sure you have working CO and smoke detectors.

On 2020-09-14 by Katharine

I’m going crazy can someone please help me! I’ve lived here for a year and all of a sudden random black stuff has shown up in almost every surface from walls, to wires to pillows and bedding and I can’t take much more. I bleach. I clean. I do laundry almost daily now. I’m going out of my mind, now it’s in my new Ac window units!

On 2019-05-17 by Rgs

Black powdery substance found in the carpet against the wall. Reappeared at the exact same spot after cleaning it the previous day. Any idea what it could be?
IMAGE LOST by older version of Clark Van Oyen’s Comments Box code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2019-03-05 by (mod) - get rid of cat pee odors and stains

See

• ANIMAL STAINS & MARKS in BUILDINGS
• ANIMAL or URINE ODOR SOURCE DETECTION
• ANIMAL or URINE ODOR REMOVAL

On 2019-03-05 by Creiiator

Hi there,

Recently this stuff has started popping up in my carpet in areas my cat tends to pee. It disappears when I spray it with pee cleaner but pops back up in a few days.

I have unsuccessfully been trying to find out what this is. If its mold or not. I have attached a picture
IMAGE LOST by older version of Clark Van Oyen’s Comments Box code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2018-07-08 by HJ

Is this mold or something else? It's dry and hard to touch, tried vinegar and baking soda, tried Tilex, tried scrubbing, brushing, etc.

Tested scraping off a bit with flat screwdriver, that worked. It isn't behaving like mold.

IMAGE LOST by older version of Clark Van Oyen’s Comments Box code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2017-08-31 - by (mod) -

Shane,

I can't guess from just this text; but it sounds as if there could be water stains or mold. You're welcome to send us a photo or two for comment - use the page bottom CONTACT link

On 2017-08-31 by Shane

I removed some ceiling plaster/drywall under a horizontal heating duct that is running under the second floor bathroom during a kitchen remodel. The joist bay was blackened. The house was built in 1920. I'm not sure what the original furnace used as a fuel. We now use natural gas. Is this typical?

Could it just be soot? There were some signs of minimal rusting on the duct and it does run below a bathroom that may have had a leak at some point in the past. Should I be concerned?

On 2017-01-14 - by (mod) -

Nicole

Often a bit of Cladosporium sp. (mold) grows on grout or trim in and around showers, and perhaps some other dark molds.

The total quantity in area, if that's all there is, is trivial and would not explain a health concern. I agree it looks horrible. Try a bathroom spray grout cleaner, maybe with a bristle brush to do some cleaning.

If there were leaks into the walls or ceilings in the bath (or anywhere) that might on the other hand be the source of a more serious and hidden mold problem.

"Black mold" is an unfortunate phrase touted by both media and marketers, since there are millions of mold genera/species, many of which are not black or dark and many of which are just as problematic as "toxic black mold" - they're just green, gray, red, white, brown, yellow or some other colour.

Search InspectApedia for BATHROOM MOLD to see details.

I don't assume an illness complaint is necessarily all in one's head or psychosomatic. Take these concerns to your doctor.

On 2017-01-14 by Nicole-marie Vasquez

I built my house two years ago and notice that the white molding on the wall attatched to the outside of my shower has black or dark brown "stuff" on it. Seems to be getting bigger as the days go by. I have scraped it off but it seems the white paint underneath it is not longer white.

A few days later the stuff is back again. It isn't in small blotches like I see in pictures of black mold, its just a glob of something dark. I am concerned because A. It looks horrible, and B. I am a stay at home mom. I have noticed the more time I spend home the more I am tired all the time and seem to always have a stomach ache or something bothering me. I am the only one in my house of four showing these signs so it could just be all in my head. What do you think?

On 2015-11-05 - by (mod) - I have a cat who is constantly urinating on the carpet

Kim:

You can read (by searching InspectApedia on HOW TO KILL MOLD that bleach is not really necessary and can create other hazards.

I'd be more concerned that you are stirring up asbestos-containing debris - that may be the case on an older vinyl-asbestos or asphalt asbestos floor that is in poor, crumbling condition.

Search InspectApedia for ASBESTOS FLOOR TILE HAZARDS to read those details.

On 2015-11-05 by Kim

I have a cat who is constantly urinating on the carpet and I've decided to replace the carpet that she has urinated on the most. I was advised to pull out the old carpet and padding and cover the subfloor with "Kilz" (an oil-based primer that seals out odor and stains) before the new carpet gets installed. I did that today and found that, under the padding, there appears to be old linoleum tiles (or something similar) over a concrete subfloor.

Whatever it was, it is now very black, flaky, and brittle (it almost looks like its charred/burnt). In some areas, the carpet pad seemed almost "glued" to this stuff

The remnants of the padding on the floor gave the same spongy appearance that mold often does. Combined with the black, burnt-looking nature of whatever linoleum-like material that was between my carpet pad and subfloor, I am very worried about whether or not it is some type of toxic mold.

To be safe, I sprayed it all with bleach. Nonetheless, I am worried about the possibility that I may have tracked it all over my house! The area is roughly 6 feet x 15 feet. I live about 6,000 feet above sea-level in a very dry climate. The house is about 35 years old and the area I'm concerned about is above-ground and not near any pipes or plumbing. C

ould you let me know me know if what I've described sounds like it could be related to some type of toxic mold? If it matters, I have never noticed any prolonged wetness in any of the areas that my cat has relieved herself.

I am also curious about whether or not cat urine is conducive to toxic mold development. Oh, I should mention, the back side of the carpet itself did NOT show any signs of mold, per se. I could definitely see the outlines of the urine stains on the back of the carpet but these were the typical golden/brownish color that I have seen in the past from my cat. Thanks in advance for your help!!!

Question: My pest company says I should hire them to treat this area for toxic mold - can you advise?

My pest and termite control service conducted an inspection today and pointed out (again this year) that the exposed beams in my basement had various degrees of fungus on the exterior.

They suggest a one time treatment with Boracare which includes a warranty on re-treatment at no cost. The price offered was $1000. Apparently they have a standard $1500 treatment charge for a basement (no partial treatment) and they warrant the work for as long as one owns the house. They are reputable firm and have been in business since 1992.

The basement is roughly a 3000 sq. ft. walkout and about 60% is exposed beams in separate rooms. One room which is always closed with no windows has no fungus. The edges of the 2x12 beams and some of the sides have white rot. Some spots have a darker brown fungus or almost black. The remaining 40% of the basement has either drop ceiling tiles or drywall (about 50/50).

My question is whether this is worth treating. The house was built in 1985 and is in good shape. We intend to move within 3-5 years.

Several photos are attached. The edge of the beam in photos 2& 3 is supposed to be white rot. The first picture is under a bathroom and shows water stains and apparently there is a darker fungus in this area.

Thank you for your review of this for me. - V.M.

Reply:

V. I found only one photo with your note - it is displayed above.

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with leaks and mold. I am left very nervous about your pest company's little jump onto the mold bandwagon with just the evidence at hand, and question further whether or not those folks are really qualified to inspect for or cure a problem mold contamination. My worry stems from

• an innate conflict of interest between the person telling you your home needs "treatment" and the company who will profit by providing that treatment - in this case one and the same person
• a suggestion of lack of expertise I read from the superficial inspection, vague diagnosis, and the fundamental misunderstanding of "treatment" - if your home has a mold contamination problem the proper approach is to find and remove the problem mold, then fix its cause.
  
  "Treatments" such as mold killing sprays are a band-aid approach that does not treat the real problem and risk leaving harmful particles in the home along with the original cause of mold growth still remaining, and perhaps the more significant mold reservoir (if there is one) still in place.

Those gripes expressed, I can't see what I could confirm as mold in your photo;

I see or think I see in your photo (above)

• what looks like some vertical white leak stains on the joists
• what looks like white leak stains (with just this photo in hand, one must question the assertion that this is white rot) on the front most edge of the joist in the upper section of the photo
• darker narrow leak stains (?) at the plywood to joist intersection in the center joist in the photo - if so there has been a leak and looking carefully for mold is appropriate;
• a small black area on the center joist - trivial in size and uncertain in material - if there is a lot of such stuff in this building it might be worth a tape sample to take a closer look.
• an HVAC duct below the [possible] leak area - if there has been a building leak it would be appropriate to inspect the duct interior for debris, contaminants, water leak entry

I'd need to know more about the building to have a sound opinion about what your photo means and about whether or or not more extensive or expert inspection (and perhaps testing) would be appropriate.

An expert would consider not only what she/he can see, but also the leak history of the home, its construction materials and details that increase the risk of a hidden problem, the results of occupant interviews (health risks, building-related complaints), and more information in arriving at a reliable assessment.

But by no means is it appropriate nor justified to always hire an expert.

At MOLD / ENVIRONMENTAL EXPERT, HIRE ? we offer suggestions that should help decide if further investigation is warranted.

Question: brown snake like stuff hanging around our basement perimeter

I have a ledge along the outer perimeter of my basement. I saw a brown dangling snake like looking "something" coming out from the finish woodwork of the and the lip covering woodwork appears to be rotting. Is it mold? Is it correctable? - concerned homeowner 5/27/11

Reply:

Sorry but with just your description I can't even hazard a guess. It could be a root from a nearby plant, or in some cases a fungal growth. Try sending us a photo using the CONTACT link found at the ARTICLE INDEX the bottom of this article and I'll take another look.

Question: what about health problems, head aches ?

What about Health problem? I have had head aches for a long time please answer this comment. Thank you and God Bless Nancyjane - Nancyjane Harvey 7/27/11

Reply:

NancyJ H.
This page alerts readers to stuff in buildings that is sometimes mistaken for harmful mold. But I'd agree that some other non-mold stain sources in buildings could be very serious problem indicators, such as

- evidence of soot leading to discovery of an unsafe heating system

- animal stains in a building where people have animal allergies

- chemical stains from improper use of chemicals

Details are at the article titled STAIN DIAGNOSIS on BUILDING INTERIORS (link at the ARTICLE INDEX the bottom of this article )

Question: black stuff coming out of A/C ducts

I have BLack stuff coming out of my air conditions ducks from the ceilings what type of mold could that be. - Dianne 8/17/2011

Reply:

Dianne, it may or may not be mold - often not.

Search InspectApedia for or click on THERMAL TRACKING Indicates Heat Loss (link at the ARTICLE INDEX the bottom of this article ) and within those articles on dark indoor stains, see the article titled "Stains HVAC Supply Registers" (or search InspectAPedia on that phrase) to see photos and read text about mold and other black stains around air supply registers and ductwork.

Question: crystallizing substance coming out of my walls - looks like white cotton

Hi, I have crystalline substance coming out on my Kitchen and bedroom wall (adjoining to kitchen) just above floor. From distant, it appear like white cotton. I remove it in morning and by evening it is again there. Moreover, i am also observing black and pink colored spots on these walls. Is it mold ? It is a new apartment. - Deepak Ladha 8/27/11

Reply:

Deepak,

I can't identify mold or not from your comment, but "crystalline" doesn't sound like mold to me.

Search InspectAPedia for the article titled Efflorescence & white or brown deposits to read about what you are describing.

Question: suspected mold on shower tiles in our rental house and mushrooms in the basement block walls

We have found two things that we suspect is mold in our rental house. The first is mold coming from between the tiles in the shower, which sprouted slimy gray mushrooms shortly after we moved in.

The second is growths of small clusters of yellow mushroom-like clusters pushing through the painted cinder block in the basement, particularly in one corner of the room. We live in Arizona and do not experience great amounts of rainfall that would cause excess moisture in the basement.

My concern regarding the mold in the shower is that the property manager shrugged it off as something to be remedied with grout. Is that enough, or should the affected area have the tiles removed and any underlying mold removed?

The second is that he was scratching the mushroom-type growths from the wall in the basement and pulling off the peeling paint (that is pushing out from darker black spot growths in the same areas) and dropping everything on the floor.

If it's mold, doesn't that risk spreading spores through the area? Thanks for any insight you can provide. - Tina 9/26/11

Reply:

Tina,

Usually mold growing on bathroom tile grout joints is trivial in quantity and not a health issue; but if you're seeing mushrooms sprouting that suggests that there is a larger hidden problem in the wall, perhaps a wet wall cavity. Same for your basement walls.

Clean up the debris dropped on the floor.

See MOLD EXPERT, WHEN TO HIRE (article link at the ARTICLE INDEX the bottom of this article ) for help in deciding if further investigation is justified.

Question: black substance at bottom trim of windows at wood-to-glass juncture

I just moved into an apartment and most of the wood windows have a black substance on the bottom trim where the wood meets the glass. In fact, many of the windows no longer have any "finish" left on that part of the window. The apartment is generally filthy from the previous occupant, looks like very little cleaning was ever done while they lived here. Should I be concerned about this "mildew/mold"? - Jeff 10/7/2011

Reply:

Jeff often we find a small area of mold growth at the inside bottom of windows where condensation keeps the window gasket or frame wet. The total area of mold formed by such areas is trivial and would not explain a health concern, but high indoor humidity and poor building maintenance mean you can't rule out a more significant problem elsewhere.

See MOLD EXPERT, WHEN TO HIRE (article link at the ARTICLE INDEX the bottom of this article ) for help in deciding if you should go further.

Finally, FYI, there is no mildew in buildings. Mildew is a small subset within the mold family and the two mildew groups grow only on living plants.

Question: light sandy colored dusty substance on the rooftop of my car returns 12 hours after wipe off

I'm searching for answers on a light sandy colored , dust like substance, that appears on the rooftop of the car. Wipe it off and within 12 hours it's back.
only thing above car is the Ceiling and light fittings. Got me completely puzzled. - Alan T 10/15/11

Reply:

Alan, you'd have to send a sample of the suspect dust to a lab for particle identification, but if you are saying that the material is appearing only when the car is in the garage, I'd look first for trouble with a nearby chimney, flue, or heating appliance. - don't send mold samples to us - it'd be a conflict of interest.

Question: dark gray substance on structural brick wall

Hey! I've bought a house that was built in 1860, all brick 3 layers deep. The previous owners never tuckpointed, which resulted in me pulling all the brick out because the mortar in the middle of the wall had deteriorated in a few places. In the middle of the brick wall, some of the mortar and brick is covered in a sandy like dark grey substance. Is this a mold that grows on mortar/brick? - Luther 11/3/2011

Reply:

Luther, I'm not sure what you're seeing inside the brick wall, as there are some molds that will indeed grow on masonry surfaces (as will algae) but more likely you're seeing mineral salts from moisture that entered the wall.

You are describing (I think) a three-wythe thick brick structural brick wall - at intervals, perhaps every 5 courses depending on the wall mason and design, bricks are laid across the three wythes to tie the wall together. Walls of this design expected the outer wythe/layer of brick to act as a rain screen - water that leaked into the wall was expected to run down the wall and exit (perhaps at weep holes) at the wall bottom.

So you wouldn't want to convert the wall to solid brick and mortar masonry during your repairs.

Watch out for bulged, cracked, or broken bond courses in structural brick walls - a serious defect that threatens collapse.

Search InspectAPedia for "Brick Foundation & Brick Wall Defects, Failures, Collapses" to read about these walls.

Question: white attic mold looks like snow, in circular patterns

Hiya there is some white mould on the beading in my attic, its white like snow and as circular pathes of whiter , i cannot see any black in there, iam worried that this is dangerous as my attic as been converted into a badroom and fitted wardrobes, there is nothing in the bedroom part are the wardrobes,

but as soon as you go bhind the wardrobes were its the bear brick n roof the mould is growing on all the beading on the roof. its not thick and starts off alot and as it goes up the beading it goes smaller. - Trudy 11/7/11

Reply:

Could be a fungus, or water leak stains. Take a look

at MOLD / ENVIRONMENTAL EXPERT, HIRE ?

Question: Cold storage room in basement seems to get musty and stuff stored there gets moldy

We recently finished our basement. The only room that was left unfinished is a "cold storage" room with cinder block walls and a metal ceiling. The room that shares a wall with the cold storage is our office, and is drywalled and insulated. It is also heated centrally with the rest of the house.

The cold storage room is directly under the garage, and is really cold during the winter. We noticed condensation on the metal ceiling during the winter and found mold on a mattress that was stored in there. The room also had a musty smell. We don't have any other soft surfaced things in the cold storage room, and cannot see any other mold on the walls or ceiling.

The mold on the mattress was black, white and tan, and pretty dense. What do we with this space? Needless to say, we pitched the mattress, putting it in a plastic wrapping first. Installing a ventilation fan would require drilling into the foundation of our house which will cost a few thousand dollars that we do not have. Suggestions? - Karen 11/30/11

Reply:

Karen, once you've removed all mold-friendly materials from the cold storage room you've reduced the propensity for mold growth in that area. What else makes sense?

First make sure there are no foundation leaks sending water into the space. If there are such leaks they need to be corrected.

You may need to install a dehumidifier, a small one that can reduce the humidity without making the space warm. IF you connect the dehumidifier to a drain it can run unattended.

A vent system that flowed sufficient air through the cold room might pick up its moisture and redistribute it through other house areas even as it reduced visible condensation in the cold room itself. Depending on the total amount of moisture and size of the cold room (if it were comparatively tiny) that might be ok but I'm worried you might just be moving a moisture problem from one space to another, and also that your cold room will no longer be cold.

Your cold room might remain adequately "cold" while no longer having a condensation problem if you insulated its surfaces with a moisture-resistant foam board.

Reader follow-up:

Thanks for all of the information. We could care less if the room remains cold, we have been storing overflow storage in there, merely because it offered extra space. We don't have anything in that room that needs to be kept cold. Does this change anything? I was worried insulating would just hide the problem, or give the mold more material to grow in. Can we use the moisture resistant foam board over the metal ceiling surface? Thanks for your help!

Reply:

Karen: ok; if the room doesn't have to be kept cold, running a dehumidifier, plus the effects of the heat output from the dehumidifier will make an easier time of reducing the condensation problem there.

Insulation does not necessarily hide the problem - I'd oppose that too. But if, for example, you insulate a chilly masonry wall with 1" High-R foil-faced insulation board (covered by drywall if it's an occupied space, for fire safety) then you effectively assure that the wall surface temperature no longer reaches the dew point - condensation on those surfaces stops. You can affix such materials to masonry or metal. Just be sure the metal ceiling is dry before the installation; trapped moisture would mean rust.

Question: mold on hardwood floors

what would mold look like on hardwood floors? Barbara - 12/29/11

Reply:

Barbara, take a look at the photos

at MOLD GROWTH ON SURFACES, PHOTOS

Question: white powdery stuff appears on my stuff every day

Since moving into my apartment a year ago, my possessions are covered daily with a very fine, white powdery substance. It returns almost immediately after cleaning, and finds its way into cabinets, closets, and sealed containers. I think it's killing my electronic equipment, too. (Four items to-date, but the CD player can be sufficiently cleaned so that it works again for a while afterward.)

The carpet was new when I moved in, but the problem is worst in a hardly-used room, despite regular vacuuming. It abated over the summer, but returned with fall and its attendant closed windows and baseboard heater use (which looked clean, but have been partially disassembled and vacuumed). A mold culture was negative. I want a lab test to identify the substance. Do you agree, or have alternative suggestions, please? Thank you, Mary Jo - Mary Jo 1/19/2012

Reply:

Sounds as if you need to track down an unusual dust source - maybe being distributed by central air or warm air heating. Try sending a dust sample to a forensic lab for help with identifying the dominant particle in your dust - as that may help track down the source. IF the lab says your dust is mostly skin cells and fabric fibers, that's typical for house dust and means you need better housekeeping or better air filtration in your home.

See HOUSE DUST ANALYSIS for some suggestions.

Question: strange growth on bath shower tile grout

Hi there, we have a strange growth in the bathroom that appears to be coming through the grout between the shower tiles. I started out as a tiny little red spot but over night grew into almost a golf ball sized yellow blob. The yellow blob looked like yellow filler foam or even sticky honeycomb. When we poked at the yellow blob, we noticed that the red colour was still behind it and had grown into a veiny/branchy pattern. Unfortunately I can't send a photo since we poked at it and washed it away before I found your website - but does this sound like anything you recognize? - Michelle Ferguson 1/24/12

Reply:

Mold growth is common on bath tiles or tile grout; if there is no leak in the wall or ceiling, the proper response is better bathroom cleaning with normal household cleaners, and improved bathroom exhaust venting.

Details about what to do, health concerns (rare) are at BATHROOM MOLD

Question: spots on my ceiling keep coming back

I get spots on my dry wall ceiling, that wipes off, but comes back within a week. - Molly 2/28/12

Reply:

If it's mold, look for a leak or moisture source. Just wiping off mold won't prevent its return.

Question: car dashboard air vents seem to be growing mold

My car windshield was replaced two years ago. Since then, I have noticed that white looking puffy marshmallow mounds have formed on the dashboard air vents. Furthermore, in the years that I owned the car, I was not very savvy about how to wash a car properly and often times would wash down the carpets of the floorboards with a hose (for a few seconds) never allowing for adequate drying. Over the years my grey floorboards turned dark black in patches. My biggest concern are my leather seats, especially on the drivers side.

Again, not being a savvy cleaner, I would use Clorox wipes at times, which eventually ate down the leather to the suade looking material part of the seat. I also developed some tears along the side of the seat and one in the middle of the seat so I placed Clear packing tape over them to prevent further tearing. In a matter of three days, the clear tape turned black and became furry and started spreading outside the sides of the tape.

Eventually after the third replacement, I just extended the tape out, now it covered the tears and some of the exposed worn down leather. Same thing happened. Eventually, I had the whole seat covered and within a week the tape would be black and furry on 60% of the outer edges of the tape. Over the past year, my health has deteriorated whereby I developed chronic fatigue, memory loss, I feel sick after driving in my car for any length, and my back begins to hurt as well. Do you think this could be mold I am dealing with? I am on limited budget so before I hired a remediation specialist I thought I would ask for your expert advice. I appreciate your time in advance. Kindly, Lisa - 3/2/2012

Reply:

Lisa,

If the problem in your car is recurrent mold growth you won't be successful in stopping it without

• finding and fixing the leak source
• finding and removing the mold contamination

Please see our articles on finding, curing, and preventing car mold beginning

at CAR MOLD CONTAMINATION

Watch out - be sure to read OZONE for MOLD OR ODORS as well, as some car mold remediators overdo the ozone treatment approach and ruin the car.

Question: black stains on concrete walls in a humid coastal climate

Hello, there is a black "stain" at the corner of a smaller room (14' x 12') with concrete walls and a concrete ceiling, located in a humid coastal area. It is at an exterior wall which can get some moisture at times, from rain. There is also a gas cook stove at the diagonal corner of the room, creating steam.

I'm not sure if this black stain is from exterior moisture, or interior cooking of meals. It was painted over, and within about two months, the stain came back through the paint. It is more vertical, at the corner of a wall, from the lower/mid area, on up to the ceiling, with some darker brownish staining on the ceiling surface, at the wall. It is mostly a grayish to blackish kind of color; darker shades in some areas. It does not look wet nor slimy.

Would the toxic form of black mold be like this, on concrete ?

Thank you for any advice!! - Mike 4/25/12

Reply:

Mike, there are black algae that grow on many masonry surfaces as well as some black or dark fungi; I can't say if your black stain recurrence as a "bleed through" the paint is due to moisture, mold, or simply not using the best paint to seal the surface.

• Try using a lacquer primer sealer when repainting
• Look outside the structure for moisture sources that may be leaking into walls
• Look indoors for soot or other debris and dust sources such as scented candles, or an oil burner not working properly (and safely)
• Look at your indoor humidity levels and how you are (or should be) dehumidifying
• Look for indoor moisture sources that you can reduce

Question: prior flood was cleaned up, now there is black stuff on windows - thermal tracking?

Your description of "thermal tracking" sounds just like what I found on the walls of an apartment. I know there was a flood of water inside, cleaned up @ a month ago. It is now completely dry. Bleach,TSP and scrubbing did not budge the stuff. There is black stuff on the windows, blinds and the worst is behind the fridge looks like dust with soot on it. Can I assume the tenant had some sort of minor fire or could that much soot appear from candles and incense? - Julie 7/26/12

Reply:

Julie if there was a flood I would look with care at the scope of work done as cleanup and beware of hidden water damage or mold. We do not leave wet drywall in place.
I'm not able to agree with your conclusion but really have too little information to speculate further

Question: mold looks like coffee grounds on our table tops

our problem is a mold that looks like coffee grounds on the table tops in about 6 inch circles all over the house--cant tell where it comes from--have checked floor vents and ducts..no ceiling vents--what is it and what causes it ? - Jon 8/4/12

Reply:

Jon, what's bigger than a duck? In other words, lots of things. With 1.5+ million mold species no one can accurately say what mold is growing in your home just by a brief e-text description. A simple tape test sent to a lab can identify the fungus for you = but more likely you should spend your money on finding and fixing the leak or moisture problem that is causing mold growth in the home.

All mold is everywhere all the time - though often at very very low concentrations. It's when conditions are ripe for a particular genera/species to flourish that that mold, or several molds, will begin to grow on a building surface.

Among the things mold needs (most need light, oxygen, something to eat, and moisture), it's moisture that's most under your control.

Question: My house in Bavaria Germany has white foamy stuff appearing

I own a house in Bavaria Germany, which is 250 years old.
In the entrance hall there are tiles and in between these tiles a white "foam" keeps appearing.
What am I dealing with?
Thanking you in advance.
Best regards
Gert - 8/16/12

Reply:

Be sure to go to Efflorescence & white or brown deposits to review our photos and text on how to recognize mineral efflorescence that is likely to be found on masonry structures.

Question: what causes a musty smell in my air conditioner return vent and how do I fix it?

I have noticed a musty smell at my air conditioner air return vent. What could cause this and how do I correct this. Thanks. - Clarence 8/21/2012

Reply:

Musty smells are often traced to mold contamination; if that's the case, moisture or leaks where they shouldn't be are the underlying problem to be found and fixed. If you see mold or mold-suspect material that is less than 30 sq.ft.. you can use ordinary household cleaners to remove the problem.

Mold removal, not "mold killing" is what's needed.

Watch out not to damage fiberglass duct insulation or liners.

Question: how do I handle green stuff on roof trusses in new construction?

They put up my trusses for the house the other day and I have noticed several areas on them that have green "mildew-ish" areas on them. The trusses were delivered tied up and it rained for off an on for about 4 days before they put them up. Can I wipe/scrub with a mold/mildew mixture? I can get to most of the trusses with use of my ladder but there is a spot or two that I can not reach. If left alone, will this continual to grow or if well ventilated, remain dormant? Please advise on this. Thanks - Green Stuff on Building Material 8/21/12

Reply:

Green Stuff:

Sure you can scrub off wood framing materials that are suspect before they are installed in the structure. I can't say from your note if it's mold or something else.

A few square inches of mold-suspect material brought into a dry finished structure won't generally increase the risk of future mold contamination, since what makes building mold contamination grow into a problem is principally moisture (and surfaces of materials that various mold genera/species like to digest, such as paper or wood). And since all mold is everywhere all the time, if your building is leaky, wet, too humid in the future, it will readily be inoculated with airborne mold regardless of the little green stuff you left on the roof trusses.

The hazard that CAN remain from even a small area of mold is that if some fool puts his/her finger into an allergenic, toxic, or pathogenic fungal colony and then sticks that finger into someone's eye, the result might be a nasty fungal infection of the eye. So don't do that.

Question: black spots in my son's room I've been told is "condensation" but now there is white fluffy stuff - is it dangerous?

I have found black spots in my sons room which i have been told is condensation, but now i have noticed there is white fluffy stuff growing on top of this,is this dangerous and what is causing it?thanx - Nadia 8/23/12

Reply:

Nadia,

What you describe could be mold; I can't say by just your note if it's "dangerous" or not nor what is the exact cause, though if it's mold, the root cause that you can and should address is water leaks or moisture. The "danger" of a mold growth in a building depends on

- the total size of the mold reservoir - not just the mold you see but all mold that is present and whose spores are easily entrained into building air; more than 30 sq.ft. of contiguous mold is enough to merit a professional cleanup

- the sensitivity of individuals in the building; asthmatics, immune impaired, infants, elderly, allergic people etc. are at greater risk

See our article MOLD EXPERT, WHEN TO HIRE for advice in deciding if your problem merits professional investigation or remediation

Question: identifying brown sand-like particles on walls and other locations

(Jan 28, 2014) Sharon said:
I was looking at a foreclosure property in houston area. I saw brown color sand-like particles on the corners of walls, on the sides and on the top of doors, inside cabinets. They seem to come off after I scrape them. They almost look like someone sprayed them on. Are these mold? If not, what type of growth can it be? Please note this house has signs of unattended animals living it in before. It smells bad. I have pictures of brown spots but don't know how to post them here. I'm thinking about bidding on the property. Your help is greatly appreciate it.

Reply:

Sharon, I just can't say from simply the description. You are welcome to email photos to us for comment, using the CONTACT link found at the bottom or top of any InspectApedia page.

Regardless of the mold concern it sounds as if the home you are discussing needs professional cleaning. Before even starting cleaning it would make more sense to have a complete home inspection so that you have a punch list of the dangerous or costly repairs that are needed and the order in which they need to be addressed.

Question: recognizing left-over marks from removal of a bee hive inside a building wall or ceiling

I just saw your image inspectapedia.com/mold/Algae_or_Mold_939_MR_DJFs.jpg
I believe these are marks left over from the removal of a bee hive. The fern pattern is where the honey comb connected to the subfloor.

Reply:

Thanks so much Michael, that's a very interesting and suggestive guess. I'll research some other hive and honeycomb marks to see if we can spot a similar pattern. Kudos.

Question: trouble removing soil or stains from porch

4/1/2014 AUTHOR:Rhonda (no email)

COMMENT:I have a problem with my front porch, it runs the whole length of the porch, tried pressure washing it, it didn't come off and seemed to make it worse.

Reply:

Rhonda,

I took a look at your photo and will also post it and comment-on it in the article on stains on building exteriors where other readers may be able to offer helpful comments

See STAIN DIAGNOSIS on BUILDING EXTERIORS

Question: Stains on Andergrove Mackay property - normal?

(July 6, 2014) Bob Ford said:
I have a property in Andergrove, Mackay that is 2 years old . The fans in some rooms have started to rust and resulted in rust marks being propelled onto the walls! Is this a normal situation?

Reply:

No, Bob, not in my opinion. Perhaps there is very high humidity and even moisture being spun off of the fan blades. Or the fan is blowing debris onto moisture-sticky walls.

Question: round outlines on ceiling: is this mold? Traced to stainless steel dust.

(July 7, 2014) Phil W said:
We have just had a new pitched roof put on our flat roof extension with the aim of making it into a bedroom. The walls have been painted. We have just noticed round mould-like grey/black hairy outlines, we think where the nails have put in the plasterboard. It is both on the adjoining wall of an older part of the house and on an outside wall, which has been insulated. Is this likely to be mould, or is it possible it's something to do with the nails. We could send a photo if that helps.

Reply:

Phil, use our CONTACT link to send me some sharp photos and I may be able to comment further.

Generally, if proper fasteners were used (drywall nails or drywall screws) then we ought not be seeing rust, corrosion, or bleed-through in new drywall installations. It sounds as if the problem is related to the fasteners or nails.

(July 7, 2014) Phil.Westwell said:
While taking the photos to send to you, I found out what it was! It turned out to be fine wire wool fibres from recently having prepared the skirting boards with 0000 grade steel wool for the second coat of varnish. The fibres floating in the air must have been attracted magnetically to the nail heads just under the surface of the plasterboard and built up over several hours to produce this furry appearance. I discovered the answer by chance: it was difficult to get the camera to focus on the wall so I held up a screwdriver for the camera to focus on it and then noticed that the fibres were coming off and sticking to the tip of the screwdriver! Maybe one of the more unusual "not mold" infestations. I'm certainly pleased that it wasn't genuine in this case – we have an old holiday house in Orkney and there are various types of mold on the older section of the house so we are a bit obsessed and jumped to the wrong conclusion when we saw the substance on the new bit.

Thanks very much for your help.

Reply:

Phil, now that's interesting and not a stain I've come across. If you could take some sharp photos to send along that'd be valuable as a future diagnostic aid.

Indeed often we examine tape lift samples of dark stains in buildings under the microscope to see what comprises the dark material - as that can point to a source. You did it without a microscope. Nice going.

I jump to wrong conclusions too - it's part of learning as admitting a mistake.

Question: what is the black stuff around door hinges?

(Sept 21, 2014) Susan of North York said:
There is a black stuff by the area where the door hinges are from top ceiling to the bottom. Would that be dust or mold. I don't have a picture to send right now.

Reply:

Susan

No one can reliably diagnose the contents of black stuff by a short e-text, but from your query one could speculate that the more likely constituents of what you describe are metal fragments perhaps along with a lubricant residue rather than mold. We might also see black or dark dust deposition at points of air leakage around a door in its frame.

Question: recurrent light dust spots on knotty pine wall paneling

(Feb 19, 2015) Lisa Schwartz said:
I have light dust spots that keep re-occuring on my knotty pine walls. I have had it professionaly tested for mold but it was not mold. I wipe it it off with englis oil or murpheys soap but then it re-appears about 3-4 weeks later all in the same spots. It is starting to spread, I have no clue what this could be or how to stop it. Any suggestions on what this could be?

Reply:

Lisa

House dust is mostly comprised of fabric fibers and skin cells. If you have a tape sample examined by a forensic lab (not mine) you can determine if your dust is something unusual; also often we can identify a dominant particle which gives a clue to a source, such as fibers from a carpet aerated by vacuuming.

Question: white powdery stuff under sofa

(Apr 9, 2015) George said:
I have recently noticed underneath my sofa (bought brand new and owned for almost a year) that where there are wavy steel supports, they have a white powdery like substance on them. I understand that sofas will probably have an anti corrosion coating on metal parts, and I am therefore concerned that my initial thought of corrosion might not be the case? In most places it looks like a thin white dusting of powder, and in other areas the white powder is more crystalline in appearance though still very small in size (I initially thought this could be dust from the white material underneath the sofa). Also, I have now noticed small dots of orange in places on these supports. There is no damp smell coming from underneath the sofa that I am aware of. Any clues as to what this could be would be greatly appreciated.

Reply:

Sounds like corrsion, mineral salts, or possibly debris from the cushion stuffing. Without a dampness issue and without visible mold I'd not be too worried. If you want to know what the material actually is

first look with care visually using a good light for obvious sources that could drop the powder onto the surfaces

Second collect a tape sample to send to a forensic lab.

Question: dust bunnies vs. condition of ceiling insulation in dry dusty regions

x (May 16, 2015) MayaRao said:
We are waiting for an answer on a short sale house that has some ceiling insulation removed from the attic and left to air in the garage. The property disclosure statement says that a small leak was fixed. When I look at the removed insulation and the space in the ceiling I see lots of dust and dust bunnies. The insulation feels loose and dry to the touch not squished like something that was once wet would look/feel like. I know only an onsite professional inspection can give a definitive answer but I am wondering if I should be worried or it is just very common to find dust and dust bunnies in insulation in dry dusty regions like the southwest.

Reply:

Maya we don't know enough from your e-text to essay even a guess. If you are a buyer and are purchasing the home with help from an *independent* home inspector (one who is actually working for you not his or her referral source) then that's a question to post to the person who is on site.

Certainly insulation can have been wet without showing that event, and wet-insulation mold risk varies by insulation type. Search InspectAPedia.com for "Insulation Mold" to read details.

Question: anyone ever heard of tests to determine whether or not a substance is mold

(May 19, 2015) Drew said:
Great website! I was wondering whether if you anyone on this site had ever heard about completing any tests to determine whether a substance was or was not mold. I am particularly interested in determining whether a something on a wall is dirt (soil) or fungal growth, and I had read that you can add a droplet of bleach to your suspect substance to distinguish. The bleach will readily be taken up by the mold and be stained while soil would most likely remain its original color. I've also been able to use a portable microscope with 120X magnification and have been able to see mycelium, but at times this is also hard to distinguish between dust/dirt/hair. Thanks!

Reply:

Drew

Yes, in our own lab we've performed thousands of forensic tests of materials both to identify the material or when it's mold, to identify the mold. (Please do not send samples to our lab.) The "bleach" test is nonsense. Plenty of materials will respond to bleach by a color change. "Soil" is a bit of a broad term for me. "Dirt" on a wall could for example be oil and skin cells from a human or pet, smoke, or other deposits. And no, I'm doubtful that 120X is sufficient to identify the particles you ask about. I'm typically looking at 400x to 1200x and make use of polarized light, phase contrast microscopy, and other methods such as microchemistry.

Finally: in mold samples we may not see mycelia, we may just see spores, or fragments of fungal material.

See MOLD APPEARANCE - WHAT MOLD LOOKS LIKE

Question: identifying stuff found under the kitchen sink cabinet

(May 22, 2015) (mod) said:
Mike said:
Found this under the kitchen sink cabinet after ripping up the cabinet liner, from some old leak that was fixed before we bought the place... there is no active leak here. Is it cosmetic mold or something to be worried about? Do you suggest simply using a mold/mildew inhibitor paint over it? Or just put a new liner and let it be?

Reply:

MIke I looked at the two image files you suggested - I see what looks like fungal growth on particle-board. The proper repair would be to remove and replace that material. If you wanted to try a less-reliable approach for a case where the trouble to remove and replace this would be enormous, if the material is dry and you can access all sides you could clean it and coat it with a fungicidal sealant or a lacquer primer sealer.

What does mold look like on or in a building?

Be sure to see our full article: WHAT MOLD LOOKS LIKE that has photographs and descriptions of what real mold looks like inside a building.

But be careful, some of the most problematic common indoor molds, the Aspergillus sp. and Penicillium group can be very light in color and hard to see on building surfaces.

We offer tips on how to look for mold for these hard-to-see molds too:
See MOLD in BUILDINGS

If you need to see what other indoor allergens look like in a building contact us (our contact information is below and at the ARTICLE INDEX the bottom of this article ).

 

Articles on Stains or Stuff Mistaken for Mold

• MOLD APPEARANCE - STUFF THAT IS NOT MOLD
  • BASKETBALL MOLD SYNDROME - BBMS
  • EFFLORESCENCE SALTS & WHITE DEPOSITS
  • THERMAL TRACKING BRIDGING GHOSTING
  • STAINS in BUILDINGS, FAQs

...

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question:

AUTHOR:bennettboyone (no email)

COMMENT:What's this white crystal substance building up in the corner of the wall

Reply:

EFFLORESCENCE SALTS & WHITE DEPOSITS

...

Continue reading at MOLD APPEARANCE - STUFF THAT IS NOT MOLD or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• MOLD APPEARANCE on VARIOUS SURFACES - INDEX to return to the full list of photographs of the appearance of mold on various building materials & contents.
• STAIN DIAGNOSIS on BUILDING INTERIORS
• STAINS on & in BUILDINGS, CAUSES & CURES

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STAINS NOT MOLD, FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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