Carpet stain diagnosis, cure, prevention guide: this article provides an orderly and thorough approach to identify and diagnose carpeting stains in buildings focusing on the causes of these carpet stains.

We describe mold stains on carpeting and also other sources of carpet stains that may otherwise be hard to diagnose.

Our page top photo shows stains on carpeting left when a storage cabinet was moved. Further inspection for water damage, leaks, and mold would be appropriate if you see marks like this.

Diagnostic Dictionary of Spots, Stains & Marks on Carpeting

This carpet stain photo shows dark, uniform stains appearing along the edge of a carpet at the building exterior walls. This location and pattern suggest an air leak at the floor-wall juncture - something easily verified by simple examination below the carpet. This particular stain pattern is explained

at CARPET AIR LEAK STAINS at WALLS

[Click to enlarge any image]

Of course there are many other possible causes of carpet stains, and stains appear in all colors from light to dark, and in all sorts of patterns. The stain color, location, pattern, timing of occurrence and other factors can help figure out what's going on and how to stop it.

6 Diagnostic Procedures for Carpet Stains

To identify, remove, or prevent annoying stains on carpets and rugs we take an organized approach by listing five stain diagnostic procedures:

1. Carpet stain appearance, shape, color, texture, pattern and size
   
   Details are at CARPET STAIN APPEARANCE
   
2. Carpet Stain Timing & History - when did the stain first appear
   
   
   See CARPET STAIN TIMING & HISTORY
3. Carpet stain location - where it appears on carpets or rugs
   
   See CARPET STAIN LOCATION
4. Carpet environment under, above, and around the carpet or rug: possible sources of staining materials including building activities, history, or events
   
   Details are at CARPET ENVIRONMENT as STAIN SOURCES
   
   What events at or occupants in the building might be stain sources: cleaning efforts, children, pets, spills?
5. Carpeting materials - or rug or padding materials and their role in accumulating or resisting staining
   
   See CARPET MATERIALS AFFECT STAINING
6. Carpet stain test & analysis: distribution of stain across carpet fibers from top to bottom, stain material or chemistry.
   
   Who has examined samples of the carpet from both within and outside of the stained or damaged areas? Did the forensic examination report on the metrics of the appearance of the stain: that is, it should be perfectly obvious, by close or even microscopic examination, whether the damage or stain is originating from the top surface of the carpet or whether it's coming from below.
   
   What was observed on the padding or underside of the carpet itself in and out of the stained areas What characterization of the stained or damaged areas was made? Is this a bleach out loss of color, a spill, animal activity or something else
   
   Details are at CARPET STAIN ID TESTS
7. Compare your carpet stain with our photos: this article series provides a collection of photos that are on all of our pages, organized by cause, color, pattern, age, etc.
   
   Some general examples begin immediately below on this page and continue through this article series, including more examples found
   
   at CARPET STAIN DIAGNOSTIC PHOTOS
   
   Often such stains are mistaken for toxic indoor mold. While mold will indeed grow on carpets in a variety of colors and genera/species, many carpeting stains are not mold at all. Mold-stained carpeting is identified and explained
   
   at CARPET MOLD STAINS

Carpet Stain Appearance: Color, Pattern, Size

Stains on carpets and rugs appear in every imaginable pattern, color, and shape, but many of these can point to a probable cause.

First let's ask when the stains first were noticed. What events that could be a stain source preceded that observation. Did someone "clean" or treat the carpeting? Did someone's pet spend time in the building? Was there a cooking event, a party, or an oil-burner puffback explosion?

What color is the carpet stain

• Black stains may be from soot sources, fireplaces, scented candles, or dirt from foot traffic, or from mold on spots where water or food were spilled.
• Brown or black stains may be from pet urine or from mold on spots where water or food were spilled.
• Green stains - often from mold growth in areas of prior food spills or wet areas
• Red stains - found on carpets are left by iron objects left in contact with wet carpeting. (Stone 1983). Red stains on carpet may also be yeast or other species of mold on spots where water or food were spilled.
• Yellow stains may be from spills or pet urine,or from mold on spots where water or food were spilled.
• White stains may be from bleaching agents or cleaners and may appear long after the cleaner was first applied or, less common, white efflorescence from water leaks or other spills.
  
  

Really? Well no. The chemistry of interaction of carpet materials and its padding with various materials that may be spilled, put deliberately, or tracked onto a carpet is complex; spilled milk may behave differently on a wool carpet than on a nylon or other synthetic fibre.

See also MOLD APPEARANCE - WHAT MOLD LOOKS LIKE - what indoor mold looks like in buildings and where we include links to example photos of black, brown, green, red, yellow, and white molds that are common in buildings.

See also EFFLORESCENCE SALTS & WHITE DEPOSITS

What are the carpet stain pattern and size?

Some stain shapes and patterns are suggestive of spills, leaks from below, pet urine, splashes, plumbing leaks, prior building floods, even prior carpet cleaning efforts.

Take a look at these types and patterns of carpet stains or spots, sorted by general size and appearance.

1. Small spot on carpet (illustrated above) are more-likely to be a splashed or dripped material.

Above: a large greenish-black stain on carpet in a closet developed under damp laundry and was found to be mold contamination.

Below: another large greenish stain on carpet with fairly defined edges, more-likely to be from a spill and an effort to clean it.

2. Big spots (illustrated above) pet stains, spills - bigger than just an inch or so, are more-likely to be a major spill that is remembered, or a clandestine or night time peeing operation by a naughty pet

3. Spots with sharply-defined edges on carpet (illustrated above) are more-likely to be from a spill than from a spray-cleaner, though rubbing cleaner across a spill or stain may blur its edges.

3. Streaks or dribbles on carpet (illustrated above) are often caused by splashed food or drink, or if regular in direction, by dragged furniture or by urinating pets that have poor bladder control. .

Above, the carpet mold staining pattern shows the footprint of furniture, possibly a stereo stand or bookshelf that sat on this floor for a long time. It's possible that the floor was wet or that the furniture was put back in place after carpeting had been "cleaned" but before it was dry.

4. Lines that are narrow and well-defied - (illustrated above)
   
   are often an indicator of furniture or other objects left on the carpet or rug surface that was wet or subject to a spill or flood.
   

   Air leaks and thermal tracking (illustrated below) also can produce very regular and well-defined stain-lines along carpets; in this case the location of the lines along walls is an important clue.
   

Above: air leaks cause this regular line of dust and dirt deposition parallel to the home's walls, usually an exterior wall.

See details at CARPET AIR LEAK STAINS at WALLS

Below: small spots and foot traffic wear on a wall to wall carpet.

The worn, darkened area on the carpet above shows significant wear from foot-traffic. Those three smaller spots are more-likely to be from a drip or spill.

5. Wide pathways or Footprints - (illustrated above) from foot traffic, building floods, air movement, soot sources
   
   Carpet stain locations, including noting stains at natural walkways, are addressed separately
   
   at CARPET STAIN LOCATION

The large stain above originates at two walls in this room, spreads into the room, has rounded edges; we suspected that there had been a plumbing leak or other water source nearby.

Below: after she "cleaned the carpet" this InspectApedia.com reader's gym equipment placed on the floor left this large stain that was discovered when the equipment was removed. Discussed at CARPET STAIN DIAGNOSIS FAQs.

6. Large areas of a room - (illustrated above) events affecting large or even entire areas of a carpet or rug are more-likely to be traced to a building event such as a flood or party, or to air movement patterns
   
   Watch out: when you suspect a plumbing leak or building flooding there is risk of hidden damage and/or hidden mold contamination that merits further expert investigation including of floor, wall, and ceiling cavities.

Above: light-bleached carpet stains, probably traced to the vertical blinds and sun exposure, discussed further

at CARPET STAIN DIAGNOSIS FAQs

7. Stains or Marks on Carpeting in a Regular Pattern - (illustrated above)
   
   may indicate the effects of a mechanical operation (back and forth vacuuming) or of exposure to variations in light (through vertical blinds, for example).

Carpet Stain Timing & History: When did the Carpet Stain Appear?

How long after new installation did the damage appear?

What activities on, over, near the carpet had taken place prior to that?

What is the building history of floods, fires, mold, occupancies by pets, occupancies by type of employment.

Really? Well not exactly. Five decades of building inspection and forensic investigation tell us that quite often a building condition, including a stain, has been present for much longer than occupants realize. It's normal to think that something that you never noticed before today is a recent event.

At BBMS BASKETBALL MOLD SYNDROME we report an example case in which a building owner was absolutely certain that stains on a garage ceiling were new and that they were mold that was growing in size

In fact we determined that they had been caused by a bouncing basketball that had occurred years before.

Carpet Stain History Diagnostic Questions

Lift the carpet to expose its underside

• Are there stains on the under-side of the carpet in the same locations as the carpet surface stains?
• Are the carpet backing stains larger than the stains on the carpet surface?
• Are there stains on the upper surface of the carpet padding?

Lift the carpet padding to expose the floor surface below

• Are there stains on the under-side of the carpet padding?
• If so are the padding under-side stains larger than the padding surface stains?
• Are there stains on the floor surface?
• Do floor surface stains point to a source (such as a leaky pipe, location near a window, air leak near a wall, or cracks and water entry in a concrete floor slab) ?

 

Carpet Stain Location

Where are the carpet or rug stains, what is their size, shape, color.

Taking note of just where, and in what pattern stains are found on carpeting is very helpful in diagnosing probable causes.

The most-obvious include

• Stains or wear appearing in paths or patterns of foot traffic such as centered on doorways or in hallways or in normal foot traffic patterns through rooms
• Stains appearing in localized zones where a pet or other animal urinated or defecated on the carpet
• Stains that map operation of specific equipment or that track air movement
• Stains under a window that may have been left open to admit air, airborne debris, rain or snow
• Pet urine stains on new carpet installed over old carpet padding in locations of previous pet stains, or pet stains on old carpet that was cleaned after previous pet urine events

Common Carpet Stain Sources related to Location & Pattern

Some common sources of carpet stains include:

• Soiling from normal use including foot traffic
• Spilled food or drinks
• Pets: urine, poop, or just oil and dirt where pets spend time - pets will return to the same area
• Thermal tracking & dust deposition along walls or under furniture
• Shading differences from variations in exposure to sunlight

Carpet Environment vs Stain Diagnosis

What is the history of building leaks, fires, prior occupancies, occupants, pets, damage, repairs, renovations?

What is under the carpet?

• What kind of padding is under the carpet, what are its details? What is or was its condition and age.
• What underlayment, if any is under the padding?
• What stains, clues, materials were visible on the floor or sub-floor over which the carpet padding and carpeting were laid?
• What kind of floor is under the carpet? Is this over a concrete slab, a wood-framed floor, or something else?
• What's under the floor: earth, crawl space, basement?
• Has anyone inspected the floor from below?
• If on a slab, how high is it above grade? Are there outside factors like water or roof runoff that needs redirection?

What activities in the building might affect the carpet

• Building occupants, pets, and activities: spills, type of carpet cleaning equipment,
• Activities such as cooking, use of fireplaces, other soot sources such as improperly- or unsafe-operating gas fired appliances
• Work or jobsite contaminants or sources of foot traffic that might track in substances that affect the carpet
• Pets in or visiting the building, or invading animal pests, urine, feces, odors, physical damage
• Who cleans the carpet? Homeowners, outside companies? If the latter, where else has their equipment been used before coming into this building?

Carpet Materials & Stain Chemistry vs Staining & Stain Removal

Carpet and padding materials

• What are the materials of carpet underlayment, carpet padding, carpet itself?
• Natural fibres, synthetics, pile type, country of origin, history of storage and handling before installation
• Do any of these materials have any particular vulnerability to the environment or to particular stain sources? [Hint: the answer is yes]
• What is the age of the carpet? Older, more-worn carpets may accept and retain dirt more-easily. - Lewis (2004)

Carpet Structure and Carpet Soiling

Some soil retention studies in the textile literature may rely on methods that are inappropriate for evaluating allergen retention on carpet. These methods are used to determine the "apparent" soil on a carpet surface.

Apparent soiling procedures depend on a protocol in which white light is shined onto a carpet specimen and the percentage of light that is reflected back through red, green, and blue filters is measured by a colorimeter.31 Soiling is computed by comparing non-soiled samples to soiled samples with measurements reported as color differences.

A review of the literature by Brown et al. found that most studies of carpet soiling are based on apparent or visual methods of soiling.

Apparent soiling, however, is not directly related to real soiling.

Studies which use apparent soiling as a measure of the amount of soil retained or released by carpet may be either unrelated or inversely related to the problem of dust and allergen retention and recovery.

Using these methods, several investigators found differences in soil retention based on fiber type. For example, wool was found to have fewer soiling characteristics than nylon.32 However, no actual difference in soil retention among fibers appears to exist when gravimetric experiments are used to recover soil. - Lewis (2004)

Micro-Occlusion Characteristics

Micro-occlusion characteristics pertain to factors that affect retention of soil to fiber surfaces in addition to the trapping of particles in a fiber's pores or crevices - Lewis (2004)

Macro-Occlusion Characteristics

Benisek found that wool carpet retains less soil with increasing pile weight while synthetic carpet retains more soil with increasing pile weight ... loop carpet appears to soil more than cut pile carpet.

... loose constructions are less prone to soiling and that loop pile retains less soil than cut pile.

The wearing of a carpet can also affect its ability to retain dirt, with worn out or matted carpet releasing more dust than less worn carpet. This may no longer be the case with newer generations of carpet that do not lose fiber with wear.

The wearing of a carpet is often related to the age of a carpet but not in all cases. Wear is clearly related to carpet usage, whereas age is a less direct surrogate for wear.  - Lewis (2004)

In other research we cite below, Niemeyer (1994) discusses the chemistry of various carpet fabrics and how they respond to staining.

Woodward's article (1976), prepared for the USDA back when we were busy killing for peace in Vietnam, relates the chemistry of specific stains on carpets to the best cleaner to use to remove them, selecting among ammonia solution, carpet cleaning products, dry cleaning fluid absorbent materials, white vinegar, plain water, or hiring a carpet cleaning professional.

This material on carpet stain treatment dates back to USDA work in 1914!

All of these sources and others are at CARPET STAIN DIAGNOSIS & CLEANING REFERENCES near the end of this page.

Photo-Examples of Stains on Carpeting

Black or Gray Stains on Carpets

Soot, dirt or abnormal thermal tracking from air leaks can leave black marks on walls and on carpeting, often at the wall-floor juncture.

Look for the source or potential sources of abnormal levels of indoor airborne debris, soot, particles, dust, such as a malfunctioning oil or gas fired appliance, any other combustion sources, even a mal-adjusted pilot light on gas stoves or heaters can be a soot source as well as the oft cited candles, fireplaces, and even pets (for example lots of dog traffic between indoors and out brings in high levels of dust).

If/when we can identify an unusual source or a source producing an unusual level of particulate debris we have perhaps answered a key part of this question of the probable source of indoor soot, dust, or debris stains.

Usually it is not necessary to test stains such as the one in our photograph to understand the cause and cure of the trouble.

Watch out: black or sooty stains in buildings that have malfunctioning gas fueled heating appliances may indicate that the gas appliance is producing dangerous, even fatal carbon monoxide gas.

Be sure that you have working CO detectors and smoke detectors, and have your heating equipment checked promptly.

Measure Indoor Moisture Levels when Diagnosing Indoor Stains and Soot or Debris Deposits

OPINION: even in a relatively clean home, unusually high moisture levels may result in noticeable levels of dust deposition on indoor surfaces, regardless of the dust source, and even including normal types and sources of house dust.

If moisture levels are a factor in the home, say moisture regularly above 55% RH, we would expect to see more-stained surfaces on those building surfaces that are more likely to be a bit higher in moisture, such as cooler surfaces on walls, ceilings, or in closets or cabinets where temperatures are lower and moisture may condense at a slightly higher level.

Indoor Stain Diagnosis Using Air Movement Patterns

Sometimes we can identify particular sources of air movement, directions of air movement, which we can correlate with the areas where we see staining. A simple example is the higher amount of dust deposition that occurs around heating or air conditioning supply registers on ceilings and walls. Relating air movement patterns to dust or soot or other debris stains may be diagnostic.

Also take a look at a short paper we wrote on an analysis of suspect indoor dust,

at An Investigation of INDOOR HOUSE DUST DEBRIS where we determined that indoor dust levels which had been suspected of originating in an HVAC system were actually carpet dust and fibers.

Pet Stains on Carpets

What about pet urine or poop stains on carpets or rugs?

Those stains will of course be found in homes where there are or have been indoor pets, and they tend to be round or oval and tend to be located in the same area, as once an animal urinates or leaves feces in an area the remaining odor marks that spot as their toilet. Usually you do not need to test these stains.

See details at ANIMAL STAINS & MARKS in BUILDINGS where we discuss animal marks on walls, floors, carpeting or other surfaces. We offer suggestions for cleaning, deodorizing, or removal of pet stains.

Mice pee indoors too, but you're not likely to see their pee as carpet stains.

Spills on Carpeting (& subsequent mold growth)

Spills of drinks, food, soup, or water, even if mopped up and cleaned promptly enough to leave no immediately visible mark may later produce discoloration that shows up as a stain or even as an area of mold growth. That's because of the difficulty of cleaning carpeting enough to remove all of the nutrients left in the carpet fibers by the spill.

In our photo above, the two round blotches of mold growth were ultimately explained by spills on the floor in that area.

Usually you do not need to test to identify mold stains on carpeting or rugs. Knowing the the genera and species of mold found in a building will not change the recommended mold cleanup and removal procedure. But if there is a large mold reservoir (more than 30 sq.ft. of contiguous mould) and if your doctor says that speciation of the dominant mold genera/species is useful for medical diagnosis and treatment might you need to identify the mold.

Watch out: Before testing for "toxic or allergenic mold" see these two articles

1. MOLD / ENVIRONMENTAL EXPERT, HIRE ?
2. MOLD TEST REASONS

Carpet Stains Along Walls & Under Furniture

Carpets in a building are sometimes stained right along the building wall,

particularly but not only at the exterior walls. Air leaks at the wall/floor juncture can occur due to building movement or simply sloppy original construction.

Air moving upwards through the building (due to upwards air convection currents) may draw incoming air at the wall/floor gap or cracks, thereby depositing dust and debris at that location.

The result is a dark stain at the edges of carpeting along the building walls.

Details are

at CARPET AIR LEAK STAINS at WALLS

Details about thermal tracking or "ghosting" are

at THERMAL TRACKING & THERMAL BRIDGING.

Carpet stains at edges of or under furniture: 

Similar carpet stains due to air movement, possibly exacerbated by higher moisture where there is less air circulation, may occur under couches or other furniture whose skirts or other construction details interfere with air movement, causing a lower temperature (and possibly slightly higher moisture condensation) in those areas.

In our photo at above left you can see the mark from a couch foot near the right side of the photo, cleaner carpet exposed below a floor runner, and darker stained carpeting that developed below this piece of furniture.

Blotchy carpet stains: (above)

When the furniture is moved the differences in carpet color or actual carpeting soiling and stains may be very obvious, especially where a couch skirt was in place.

Occasionally we also see more blotchy carpet stains with sharply defined edges where a spill has occurred or where a partial attempt was made to "wash" an area where thermal staining had previously occurred.

In this photo at right side a vertical dark line probably marks where a couch or chair skirt was in place.

[Click to enlarge any image]

Usually lab testing is an unnecessary approach when removing or diagnosing stains or contaminants on carpeting but sometimes when visual inspection and considering building history (leaks, spills, pets, air leaks, puffback or other soot producing events) isn't enough and where significant expenses are involved in cleaning or replacing carpeting we might test tape or dust samples of the carpet stain area as well as other samples of settled building dust.

Then see CARPET CONTAMINATION TEST PROCEDURE

Variations in Carpet or Rug Colours

Might Be Traced to Repairs, Use of Different Yarns, Methods of Original Construction, Exposure to Light, Moisture, or Water

Reader Question: Dear Inspectapedia:I am amazed by your fabulously comprehensive website. Compliments! However, I still don't find what I am looking for -- and don't quite know what to look for. alas! - and urgently need your advice.

[Click to enlarge any image]

About three years ago I bought a beautiful blue-white Peking rug from a dealer in Manhattan for my bedroom. Suddenly about one and a half years ago small whitish/light-ish, almost bleached looking stains appeared.

They slowly expanded and expanded and are still expanding. I or no one else spilled anything on the rug.

There is no moisture or leak nearby. There is no mold or mildew looking (?) and smelling stuff on the rug.

The stains seem to grow not totally wildly but somewhat straight along the web (or waft??) of the rug.

I am very, very worried by something as inexplicable spreading in my apartment and would like it inspected but I don't know to whom to turn. (I also seem to have some health problems - not respiratory though - lately. but they might be rather age-related.)

Could you please give me some advice? Of course, I would pay for the inspection if required.
I have attached some photos.

With many thanks in advance and best wishes, B.B. 15 Sept 2014

Reply: regular or rectangular or weave delineated color variations may be due to differences in rug yarns

No need to pay anyone for inspecting these photos nor the rug.

I can see one most likely explanation and offer a possible additional one for the light color "stain" patterns in your photos, provided we are referring to the light gray areas that have regular rectangular edges: this is a rug repair - re-weaving, or simply a use of a segment of yarn from a different batch that was not so dye-fast as other yarns used in the original weaving of the rug .

I've seen this exact pattern on antique, repaired rugs of various origins, especially some Moroccans.

Sometimes a spill or spill plus cleaning attempts will show up these yarn or repair differences further.

Flip over the rug and look at the back and you may see evidence of re-weaving repairs.

If you don't then I ascribe the difference to use of a different yarn at time of original weaving.
You can most likely confirm my opinion by showing your photos to an experienced rug expert in your area.

Unless you object, I'll post these photos at an appropriate spot at InspectApedia, keeping your information completely private of course - to invite further comment from others some of whom may be more expert.

Reader Follow-up:

I finally get to respond to your informative and incredibly fast reply re my rug spots. Sorry about the delay and thanks again.

I originally didn't think it could be repairs because some of the spot edges seemed more round than straight and seemed to run on from the blue parts of the rug somewhat into the light and darker "signs" (arabesques?) on it.

But then i looked again at the back of the rug and saw that they were really almost straight/rectangular. I couldn't spot whether the reason was re weaving with a slightly differently colored material because I don't know what to look for and what would indicate well-made repairs. But it is a very reasonable explanation.

However, I don't understand why the spots appear only now, after years - there definitely was no spill on the rug. And I also wonder what might have made the repair yarn, if it is that, first look exactly like the main blue color and then suddenly lighter/grey Would you have an explanation for that?

It seems that you are sure it is not microbes or any toxic material that leads to the color changes, right???

I'll try to go to the dealer, if he is still there, and ask him about the situation but I doubt that he would tell me anything.

by the way, I have another light blue rug in the apartment with off-white geometric designs. I think it is turkish. It now also seems to have lighter and darker streaks and sections. If I find the time I shall take pictures and send them if I may. I also didn't see the changes before.

Maybe it's just the light which I understand always bleaches blues more than other colors. That rug is a special case: i saw it at a dealer on a street fair and fell in love with the rare two-colored design.

When I turned it around, one could see that most of the off-white designs clearly originally were rust-colored.

So it seems the whole rug had been sun-bleached(?). I think it is gorgeous. The dealer himself wasn't there when I gave a down payment to his assistant and told me later he actually hadn't had in mind to sell it on the street but to give it to designers. - B.B. 9/19/14

Reply: why changes in rug colour may map individual sections of yarn or weaving

I'm not a rug expert, but I have some experience with these colour variations

. I've seen that different yarns will wear differently and will respond to light as well as spills differently. So a repair or even just a different yarn used in segments of a rug will often change appearance differently than their neighbors even in cases where the whole rug was exposed to the same conditions, say light, or wetting.

Sometimes it's a repair, sometimes just a different, perhaps small batch of yarn used in certain rug areas at the time of original weaving.

Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and content suggestions regarding thermal tracking and its appearance on carpets as well as building walls and ceilings.

• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional HOME INSPECTION SERVICES,        HOME INSPECTION TRAINING,        Horizon INSPECTION SOFTWARE    &    PUBLICATIONS. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home.

 

Research on Carpet & Fabric or Textile Stain Causes & Stain Removal

• Also seeReferences or Citations at the end of this page
• Bernadout, D., A. Vaughan, B. Smith, H. Abadjian, and C. Aigin. "Carpet stain removal and spotting guide."
• Biers, Karen. TIPS on REMOVING STAINS from CARPETS [PDF] Ask A Specialist 61 (2002): 1. Utah State University Extension
• Boschetti, Margaret. "EC82-2057 Carpet Care: Cleaning and Stain Removal." (1982).
• Brown, C. B., S. H. Thompson, and G. Stewart. "Oil take up and removal by washing from polyester, polyester/cotton blend and other fabrics." Textile Research Journal 38, no. 7 (1968): 735-743.
• Feather, Betty L., and Patricia Klobe. "Carpet care, cleaning and stain removal." (1979).
• Furry, Margaret Smith. Stain Removal from Fabrics: Home Methods. No. 1474. US Government Printing Office, 1942.
• Hofbauer, Brenda Hess. THE EFFECTS OF COMMON HOUSEHOLD CLEANING AGENTS AND AGING ON THE REMOVAL OF QUANTITATIVELY APPLIED FOOD STAINS FROM RAYON, NYLON, AND OLEFIN PILE UPHOLSTERY FABRICS [PDF] PhD diss., Virginia Polytechnic Institute and State University, 1982.
• Kissa, Erik. "Coffee stain on textiles. Mechanisms of staining and stain removal." Journal of the American Oil Chemists’ Society 72, no. 7 (1995): 793-797.
• Knox, COMMON TEXTILE STAINS & STAIN REMOVERS [PDF] University of Arizona, https://repository.arizona.edu/handle/10150/302931
  Note: this article focuses on stains on textiles and fabrics.
• Lang, Harold Locke. Removal of stains from clothing and other textiles. No. 861. US Department of Agriculture, 1917.
• Lewis, Roger D., and S. M. Causer. RETENTION AND REMOVAL OF HOUSE DUST CONTAMINANTS FROM CARPET [PDF] Integrating our Knowledge of Source Dusts, Carpet Properties and Carpet Cleaning for a Healthier Indoor Environment." Int. J. Flooring Sci 1 (2004).
  Abstract:
  
  The purpose of this paper is to describe the state of the science in retention and removal of house dust contaminants in carpet. A brief review of the literature on carpet contaminants, its health concerns, sources and pathways, mechanics of soiling, and cleaning will be presented. The importance of lead, dust mite and cat allergen, both as serious indoor pollutants and as divergent exposure pathways, is emphasized.
  
  Data is presented on the importance of fluorocarbon coatings, surface area, and wear retention and removal of allergens and lead. Although high-suction, high-flow rate vacuum cleaners appear to have an important role in cleaning dust contaminants, many household vacuum cleaners clean with only marginal difference.
  
  Carpet cleaning systems that remove dry particulate, lead and dust mite allergen appear to be superior or equivalent to wet removal methods in new studies. The interaction of carpet types with vacuum cleaners and with dust loading, however, suggests that a systems approach be used for addressing the removal of house dust contaminants from carpet.
  
  If carpet is to remain a staple of the indoor environment, then an understanding of the source of dust-borne contaminants and of how they are retained, released, and removed may inform the debate on how to maintain a healthy indoor environment.
  
  
• Nazari, Ali, Shahab Torabian, Majid Montazer, Mohammad Bameni Moghadam, and Mohammad Shahvaziyan. SPRAYING COLLOIDAL NANO TIO2 AND CROSS-LINKABLE POLYSILOXANE ONTO ACRYLIC CARPET FOR SELF-CLEANING [PDF] Research Journal of Textile and Apparel 18, no. 3 (2014): 51.
• Niemeyer, Shirley, RUG AND CARPET FIBERS: SELECTION AND CARE [PDF] G94-1222 (1994). University of Nebraska, Lincoln, Historical Materials
  Excerpt:
  
  A stain-resistant finish will resist many stains, but it will not resist all types of stains. It will resist most food and beverage stains, but will not resist household chemical stains such as acne medication containing benzoyl peroxide, chlorine bleaches and cleaners, plant food containing organophosphate, dandruff shampoos, and pesticides.
  
  Stains that may alter or destroy dyes in stain-resistant carpets are red wine, pool chemicals, oven and toilet bowl cleaners, and furniture polish. Many common stains can be removed by blotting with water; water and a non-bleaching, mild detergent solution; or other technique.
  
  However, the stain resistant technology may require cleaning procedures different than those used in the past, and consumers are urged to refer to the specific recommendations of the carpet or fiber manufacturer before attempting home or professional cleaning solutions. Using chemicals or procedures not recommended in the manufacturer's cleaning guides may nullify the warranty in the stained area.
  
  Manufacturers may also note that there can be slight loss of the stain resistance in high traffic areas and may exclude those areas in their warranty.
• Price, Daniel L., Brandi N. Morris, and Georgia Lagrang, ASSESSMENT OF ACCELERATED HYDROGEN PEROXIDE FOR SANITIZING CARPET [PDF] In The Annual Meeting and Exhibition 2007. 2007.
  Abstract:
  
  Carpet is a three dimensional porous flooring surface that accumulates both settled and tracked in soil and biocontaminants. Biocontaminants that accumulate on and in the pile of carpet typically consist of soil-borne bacteria or mold spores. When carpet becomes damp following a moisture event such as a spill, these accumulated spores may germinate and grow producing offensive odors and stains.
  
  An accelerated hydrogen peroxide (AHP) technology was assessed for the ability to sanitize soiled carpeting. Sections of soiled carpet were sprayed with the peroxide based cleaner-sanitizer followed by brush agitation.
  
  Following fifteen minutes of dwell time the carpet was vacuum extracted using hot water only. Enrichment cultures prior to cleaning-santizing and following cleaning-santizing demonstrated effective kill and physical removal of the viable biocontaminants.
  
  The value of sanitizing cleaning of carpet has received little focus.Most carpet cleaning product claims today center around appearance and allergen removal. Identification of chemistries that effectively sanitize carpet would improve its aesthetic and hygienic status
  
  Really? Editor's OPINION: While Price's work supports surface treatment of carpeting, in our experience in follow-up testing of soiled carpets that have been professionally cleaned, we found that no spray, vacuum, or disinfectant of carpet can remove all or even most contaminants if those are deep into the carpet or carpet padding, such as in carpeting that has been subjected to flooding, sewage backups, pet urine.
• Stone, Janis, QUICK and EASY STAIN REMOVAL [PDF] Clothing, Fabrics Labeled, and Follow These Safety Precautions. Iowa State University, estimated date: 1984
  
  Watch out: because "white vinegar" is so popular as a "stain remover" or "disinfectant", we repeat Stone's warning below. This does NOT mean that vinegar is never useful on carpet or other stains. It's widely used, for example, in rinsing pet urine stains on fabrics or carpets.
  
  White vinegar: Vinegar (acetic acid) may weaken cotton, rayon, acetate, triacetate, or silk fibers and may cause color change. If used as a stain removal agent, test on a hidden seam allowance for colorfastness.
  
  
• Woodard, Janice Emelie, and Katherine Leona Habel. CUE SHEET ON CLEANING CARPETS AND RUGS [PDF] (1976). USDA Extension Division & VPI
• Zsednai, A. "Carpet cleaning and maintenance." In Advances in Carpet Manufacture, pp. 419-442. Woodhead Publishing, 2018.

Building Air Leaks & Thermal Tracking Marks on Floor Carpeting Near Walls

Moved to CARPET AIR LEAK STAINS at WALLS

Mold Stains on Carpeting

Moved to CARPET MOLD / ODOR TESTS

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

How do I clean up a detergent spill on my carpet?

I Accidentally spill detergents on to grass and carpet in my rented house's front, two carpets,most on the ground, the owner requesting a 420$ compensation on cleaning, is it reasonable? he stated that cleanning company said normal cleanning method does not work. is it true? - 2023-11-29 by Anonymous -

This Q&A were posted originally

at INDOOR COMBUSTION PRODUCTS & IAQ 

Reply by InspectApedia Publisher (mod) how to clean up tide laundry detergent spilled onto a carpet and onto the lawn

@Anonymous,

To make a useful answer we would need a bit more infdormation.

1. What sort of detergent did you spill on carpet: brand, type, amount, size of are affected? Detergent alone might not harm carpeting, but some cleaning products might discolor it. Can you post a photo?

2. Spilling a bit of detergent onto grass outside a building, unless at industrial strength and in quantity, ought not require cleaning of any sort, though to protect the grass one might have hosed down the area.

3. Is this an area carpet that can be sent out for cleaning? or is it wall-to-wall carpeting that would normally be cleaned in-place?

4. Detergent cleaning method for spilled detergent on carpet:

If what you spilled was laundry detergent or a similar product would require cleaning with water, or perhaps warm water, in sufficient volume to dilute the detergent and to permit it to be vacummed up. That doesn't sound very unusual to me.

5. Cost to clean a detergent spill from carpet:

Typically the cost for professional carpet cleaning in the U.S. is about 25 cents per square foot or $50. to $100 for an entire room. You might think you should just pay for cleaning the exact area of spillage - perhaps just a square foot or so.

But since cleaning the carpet in the area of a detergent spill, especially if the carpet was previously soiled and also affected by the carpet material and condition, will often result in the cleaned area being noticeably lighter than the rest of the carpet, it would be common to insist on cleaning the whole carpet.

That said, the amount of compensation you quote sounds rather steep to me.

But, then, we don't really know what you spilled, where, how much, the type of carpeting, how deep into the carpet the detergent has soaked, the pre-existing condition of the carpet, nor its effect on the carpeting.

Please see

CARPET STAIN DIAGNOSIS https://inspectapedia.com/interiors/Carpet-Stain-Diagnosis.php

where we'll ultimately move your question as that's the topic page where both the information given and other reader comments will be most helpful .

Followup by Anonymous

@InspectApedia DF, also i when i bring the detergent to garbage can, it spilled a bit along the path. he stated that the detergent was dry and sip into some gaps and into the grass soil which required more costive way of cleaning. Can you provide a reasonable payment?

Reply byInspectApedia Publisher (mod) - do we need to clean up laundry detergent spilled onto outdoor grass?

@Anonymous,

There's no reason that you would need do much to clean up a small amount of laundry detergent that fell on the grass outside of a building.

And in my OPINION it's absurd to claim that you have to hire a professional cleaner for that purmpose.

Certainly it's reasonable however to add some water to that area using a garden hose.

With respect to getting an estimate for your carpet cleaning I'm sorry but I can't do that because I just don't know enough about the details involved.

I've already given you a typical cost to clean an entire room.

What are these stains on new carpet - not pets, not spills?

This carpet is less than a year old, was professionally installed by Luna along with new mats under the carpet, and was their top line for not staining. We have a high-end filtration and humidity control system and own our home (we are very neat and clean). This carpet is barely ever walked on except to vacuum it regularly. These are not pet stains or from spills.

They seem to be popping up in round patches everywhere, but only in this one room.

Luna re-carpeted most of our house but it’s only happening on this brand/color of carpet. Any idea what’s going on? - On 2022-07-16 by LJ -

Reply by InspectApedia-911 (mod)

@LJ,

With the apology that of course I can't know for certain the cause of stains based on such a limited bit of information, I have to say that the pattern of those marks really looks like let me see what their happened splashes were spills onto the carpeting.

It does not look like a defective product.

You might need to ask the installer if they can pull the carpet up and inspect its back side and the padding and floor below. If the back of the carpet and the padding below are quite clean then you know that the stain is coming from above.

On 2022-06-30 by Emma - something leaked on my carpet: how do I get rid of this ?

A box for a neighbour has leaked on my carpet. No idea what the substance was but when it was cleaned with a multi purpose spray, this happened. Any idea what it is and how to get rid of it?

Reply by InspectApedia-911 (mod) - crystalline residue left after carpet spill

@Emma,

My goodness, That looks crystalline, perhaps a salt left as the wet area dried.

Or if it's soft (can't tell from our photo) rather than crystalline or hard, we could be looking at mold growth.

I'm a little worried about mold in and under the carpet.

What was the liquid that leaked?

On 2022-04-13 by Nikki - cause of very large light brown carpet stain?

Hello, I’m needing help identifying and manning coming up with a solution to a stain I’m encountering. I live in a rental. It’s been obviously used and abused.

There was a house fire in the garage decades ago and the home owners says they replaced the carpet back then. Idk what type of carpet this is. It’s thick though.

The stain was a black tight stain at first and then I shampooed and rinsed the area.

Mid dry I noticed it looking heavy with an orange and red undertone on the corner of the entryway to the kitchen. The dryer it gets the dirtier (browner) it looks. I’m so confused and embarrassed. Any suggestions or tips would be incredible.

We also have a fireplace in the exact room. I’m sure past tenants have had pets as well. Any other kind of information I honestly don’t have unfortunately.

Reply by Inspectapedia Com Moderator

@Nikki,

That's certainly a very large brown stain and more homogeneous than one usually sees from pets.

Perhaps there was a spill or a leak or a pit. Repeatedly in the same location and someone tried to clean it.

It may be significant that it's in the traffic path for people walking in and out of the room.

It would make sense to lift the carpet and check the padding and the floor underneath. Let me know what you find.

On 2021-09-03 by Anonymous - brown stains on carpet and indoor air quality complaints: coughing, breathing trouble, odors?

Moved into a rental home & not feet well light headaches/nausea. Symptoms progressed & new ones added to them.

Every now & again I’d get a whiff of something but it was light & quick. I k ow it’s not musky and I’d have to say it’s more like chemical related.

Anyhow the whiffs I got were in living room & more in the air towards ceiling & vents are in the ceiling on first floor. I got a few whiffs above the living room in my bedroom.

One came from the fan over a vent diagonal on the floor (vents on floor upstairs. The other whiffs were to the left & right of my bed. I put a sm fan on a small table approx 5 ft from me head one nite cuz hot.

I’m midst of night I woke coughing nonstop for rest of the night & when I left in morning it stopped. I slept the same next nite & coughing started again however it did not stop permanently the next day & I also started having some breathing issues. I also got some like burns inside my nose & on the back of my lips.

It’s been lil over two weeks & I’m still like this. Docs cannot find nothing wrong. I actually have other symptoms just too much to get into. I found a stain under the table the lil fan sat on.

Once again the living rooms below where I also had few whiffs of the smell I’ve had throughout.

I noticed there’s another stain like this on the other side of the bed.

There’s much lighter stains that look nothing like these that I assume are food/beverage or pet related (I’ve seen stains like these before.

However these stains in pic seem darker than I’ve seen ect. To smell these dark stains I don’t smell nothing. However I decided to clean up good & once I got the carpet back & smelling more to try to locate this whiff I’d had before I still hadn’t smelled it.

I was swearing cuz the window was up airing out the room & it was 100 degrees so hot. I went out back for fresh hair cuz my coughing/headaches started acting up more & at this time I realized my sweat all over me smelled just like the whiff but massive!

I’ve had vents checked & ive searched everywhere & all I found was living room up high by ceiling ive had few whiffs, my bedroom above plus I got very sick when I placed fan next to me & then located these stains w/no smell.

However after pulling carpet up more & doing some cleaning g (not long) I began sweat & when went out to cool down the sweat was this smell but powerful.

I appreciate any help. My landlord will not help in any way cuz they e not been able to “smell” what I’ve spoke about. They may never smell it cuz so far I’m the only one.

Oh yeah my 10 Lb chihuahua became mentally impaired/physical pain the night I used the small fan. Approx 5 days she acted as in severe depression wouldn’t move from lay down position like starting off. I could get any response if clapped hands ect He also wouldn’t let me touching

He got up couple times day but nothing else. He’s just starting to eat a lil. He’s lost half his body weight since moving here. Okay lastly I cannot see any evidence of the stains on the top of the carpet. Thank u so much

Reply by inspectapedia.com.moderator - animal pee stain

@Anonymous,

That stain looks like one from a spill or from animal pee, but it is nowhere near large-enough to be the explanation of health complaints for building occupants nor even of a chihuahua.

Try improving the amount of fresh air ventilation in your home to see if that helps.

About your health complaints, find a doctor whom you trust and listen to her advice.

On 2021-07-05 by marishka - cause of very large round stain in carpet, not near wall

What could have caused this?

We had been renting for several months when we first moved to a new area.

We just bought a house, and so we moved out. I didn’t notice the stain until the landlord pointed it out at checkout. I assumed itt was just shadows from my vacuuming pattern. The landlord has now informed us it is a stain and sent these photos.

She says she will need to replace the carpet and take it out of our deposit.

We don’t have pets. We don’t wear shoes in the house. This area is where my husband had his desk so it’s not like it had a lot of traffic. He doesn’t recall spilling anything, but he knows to blot right away if he did. We treated this rental as if it were our own home.

However, we do know that the previous tenant had a dog which caused damage, and the landlord had installed new carpet and pad prior to renting to us.

We probably should have had the vents cleaned because we found pet hair all around the house for many months after moving in. And the HVAC filter was absolutely black when we changed it shortly after moving in.

I asked the landlord if they had treated the subfloor with Kilz or similar sealer before installing the new carpet, thinking that a pet stain could possibly seep up from the subfloor through the new carpet and pad.

While she did not specifically answer regarding the Kilz/sealant, she insists that they did not install the new carpet and pad over a dirty subfloor.

She sent me these photos and said there was lots black water after they steam cleaned, plus what looks like dog hair to me (see photo).

Again, we do not have pets. Any ideas? We’re not likely to make a fuss about this, but we are perplexed.

Reply by inspectapedia.com.moderator - rental carpet stain and debris

@marishka,

What's the source of that handful of debris in your other photo? A vacuum cleaner? What is it purported to be telling us? Pet hair? That's not a surprise given the history you report. Is there pet hair in the HVAC ducts? Air Handler? Was the air filter changed?

A dry pet stain on subfloor under new padding and new carpet might smell but wouldn't be expected to cause a visible stain on the carpet.

The pet hair - if you never had animals in the home while you rented it - would not be expected to trace from your occupancy.

The stain in the photo could be from your occupancy - even it occurred, was wiped up immediately, and then forgotten.

Sometimes those stains don't show up immediately after the event itself.

If there is a significant cost involved you might want to visit the property to see for yourself

- that the carpet was brand new when you moved-in
- that the stain is indeed in your residence (no mistake about which residence, home, or apartment)

keep us posted

On 2021-04-24 by Tracey - this light carpet deposit or stain has happened twice before: after we replaced the carpet it happened again

Can anyone help what’s causing this? This is my second replacement carpet as the 1st one went exactly the same .

Company changed it , it happened again so I paid extra for a better underlay but it’s still doing the same . It has a waxy feel to it when you rub it on your fingers .

Reply by I inspectapedia.com.moderator - waxy carpet stain reccurrence

@Tracey,

That looks to me like stains occurring from activity on the carpet.

When the prior carpet was replaced

1. Were there stains on the under-side of the carpet in the same locations as the carpet surface stains?

Were the stains on the underside of the carpet bigger or smaller or the same as the stains seen on the carpet upper surface?

2. if the padding was removed as well, was the padding stained?

Were the padding stains bigger or smaller in area than the stains seen on the carpet underside?

3. If you lift the carpet and padding to expose the concrete floor slab below, are there cracks in the slab? Are there water stains on the slab?

4. The history: that you say you saw the exact same thing on prior carpets, suggests that the problem is an activity in the building (pets, games, something shedding, leaks)

and a look at the floor and carpet padding below the carpet can confirm that it's coming from above - not from the carpet itself or leaks below.

5. When you replaced the carpet was it with exactly the same carpet as was installed before? From the same source, supplier, and maybe even from the same large roll or production run? If so there could be a defect in the product.

 

On 2021-03-15 by Laura - cause of multiple dark spot stains on carpet

Thanks for your suggestions. Yeah, we are really baffled especially since these stains appeared this last year when we haven’t even had company of any kind in the house.

I was concerned maybe the window was leaking but the soots seem to far from the source and like you said they don’t match up and the subfloor isn’t wet at all

On 2021-03-15 - by (mod) -

@Laura,

Those dark areas with well-defined edges, particularly where the color is darker near the edge, are characteristic of a spill or pet pee.

It may be that over the 18 years that you say this carpet has been in place, spills occurred, though usually when we see a cluster of spots like this it's animal pee. (Perhaps a clandestine visitor?)

The fact that the stains don't map to wet areas or stains in the padding or in the floor below are strong suggestions that the source was from above, as I've described.

Another line of investigation is that floor cutout for an HVAC supply (?) register; inspect that register and ductwork to confirm no signs of condensation or other moisture that might have exited there (or animals sneaking in from there).

On 2021-03-15 by Laura

Well we don’t have pets and nothing has been spilled in there? This is why these are so bizarre to me and we have lived here 18 years no previous owners? I’m just so baffled?Other thoughts?

On 2021-03-15 - by (mod) -

@Laura, those look to me like previous spills or pet urine spots.

Often such spots change colour over time as time + moisture changes can cause chemical changes that show up in the fibres as darker stains.

On 2021-03-15 by Laura

I wanted to add additional images

Hello, The carpet in the photos has very large stains that appeared and have gotten darker over the last year. It’s in a living room we don’t use.

We pulled up the carpet partially and the subfloor doesn’t appear stained at all below the stains nor does the pad. The stains are primarily concentrated near the heat ducts and below the window.

On 2021-03-12 by maggie_boswell - Small dark purplish spots appeared mysteriously on carpet; 1 near a radiator;

These spots have mysteriously appeared in my small dressing room.

The red ones are under a small radiator and the grey/green/yellowy ones are under 2 plastic storage boxes. We don't have any pets. When I tried to remove them with Vanish, I could detect a smell.

Reply by I (mod) -

@maggie_boswell, I sometimes see spots like that on carpet where there has been a previous spill and now a bit of mold is growing on organic material.

Course no one can be certain, from just a photo.

Sometimes were they staying is persistent we like to lift the carpet to inspect the padding below to be sure that we understand both accomplished and also whether or not there's actually a problem such as a leak underneath the carpet in the area of the stain.

On 2021-03-03 by Jimmie - protective carpet spray left stains that won't come out with cleaning

Ihad carpet cleaned and the spray that protects from stain left dark places all over.

It was steam cleaned 3 times and it's still dark For insurance to pay I have to prove that is the problem.

So I need it tested I can send a small piece please tell me what can be done

Reply by (mod) -

@Jimmie,

Sorry, but we cannot provide the carpet lab analysis or testing or stain analysis service that you asked about. We do not sell anything. No products, no services.

In order to absolutely assure our readers that we write and report without bias we do not sell any products nor do we have any business or financial relationships that could create such conflicts of interest.

However if you have before- and after-treatment photos of your carpet that may be sufficient. See what you can find; else I am concerned that a lab analysis may not tell you what's needed which is causation.

On 2020-09-22 by chrisbellco - dribble pattern light colored stain on top of the carpet

These stains appeared in the basement of my mother-in-law’s Colorado home. They are definitely on top of the carpeting. You can tell by the spot that starts on the rig and moves to the carpet. Any guesses what is causing these?

Reply by (mod) -

That looks like a spill, Chris, starting with the large area and dribbling off to the left as if a bowl or plate or container of liquid were tipped while moving above the carpet. But I'm only guessing.

On 2020-09-22 by chrisbellco

Thank you. I’ll take it. Does this image change your mind?

It’s just a couple streaks, not a dried puddle as it kind of looks like here.

Reply by (mod) -

Not sure what we're observing - that dark area (or is that a shadow) or the light areas in the dark area?

The light area looks as if something spilled in a spot and continued as a sort of dribble across the carpet.

Take care to use the least-aggressive cleaner as it's easy to leave a bleached area otherwise.

On 2020-09-22 by chrosbellco

Dan, I’m grateful. The shot stinks but your advice is spot on. Yes, I’m talking about the light stuff, not the dark.

I agree that it is on top, and I’m happy that you think it is a spill.

The house has been empty for a bit, so that’s confusing, but maybe she never noticed them before. Or maybe the stains became more visible with age.

I was wondering if it was snails or slugs, or some other animal, but I’ll happily go with the the more innocuous explanation.

Thank you again!

Reply by (mod) -

Stains can for sure appear over time, sometimes quite a while after the original spill or other cause. Could have been an animal too - maybe an old, incontinent pet. If so you'll recognize the smell as urine.

 

On 2020-09-14 by Joe - diagnose this collection of tiny dot-stains in rows of three or four

I have a tan (ish) colored carpet and these mysterious small spotty line pattern stains keep accumulating. It started slow, thought they were just spills, but there’s more now and I just know it’s not spills. Some sort of bug or pest?

Reply by Mod

Those little stains are in such regular rows that it looks to me as if someone has been playing with poking a fork into the rug.

I've also seen regular marks like this on carpet when someone walked on it with dirty or rusty spiked athletic shoes or track shoes, though IMO those spots are a bit close for somthing other than clamp-on shoe spikes for walking on icy surfaces.

I'd want a look under the carpet and I'd want to know the history of use, occupants, presence of kids, and for those larger dark gray-green stained areas, perhaps a history of leaks, water entry, or pet urine.

On 2020-08-07 by Erin S. - Yellow "shadow" stain near door, on wall to wall carpet: What caused this?

Can anyone please tell me what this might be?

Is it just filtration soiling, or something else?

How is it cleaned?

Thank you.

Reply by (mod) -

Erin that looks to me like a spill or animal urine stain. Notice that there appears to be a shadow of yellow on the lower portion of the door immediately above the stain?

That's characteristic of pet pee against a door, left by a pet who was desperate to be taken outside to relieve himself.

On 2020-08-04 by Victoria G - what caused this single round stain on my carpet - against an interior wall?

What could be the cause of this circular stain on my carpet? It's not against an exterior wall or bathroom. Doesn't feel damp. It came up gradually over the past year and is darkening. Thank you.

Reply by (mod) -

looks like pet pee, a spill, or a leak from below

On 2020-07-09 by Matt - diagnose the stains at corners of carpeting

Does anyone have an idea what thest stains are.

They're at the corners of the carpet

Reply by (mod) -

Matt

Thanks for the photo and question. I see

- a very worn carpet - light areas in doorways and other areas of heavier foot-traffic

- stains on carpet in at least two areas, both apparently at the end of a wall

- tan stains in the wall-end above the stained floor

- water stains on floor trim around the wall bottom

I can't say if this is pet urine or a prior leak in walls or prior leaks onto floor: further investigation is needed.

This does not look like a simple carpet stain nor an individual spill.

Often pets will pee on carpet near a wall or in a doorway.

Look under the carpet and let me know what you see.

On 2020-05-13 by Lori - carpet "shadows" have become full blown stains. Is something seeping up from underneath?

We bought our house about 3 years ago here in the Texas Hill Country.

For the longest time, I thought these were just shadows from the ceiling fan, but, now they look like they are full blown stains. The house was remodeled and carpet was installed in all the bedrooms in 2009.

This pic is from one of the bedrooms but, the stains all look alike.. Looks like a water leak, but, nothing like that has happened since we have lived here.

Any ideas? We have a flooring guy coming in tomorrow to give us an estimate for replacing with wooden flooring, but, I don’t want a floor to warp if it is indeed something seeping up from underneath.

Reply by (mod) - tip for diagnosing these carpet stains

Lori,

Particularly because you're considering replacing the carpet with wood flooring, there is nothing to lose and everything to gain by pulling up the carpet in a corner where these stains occur.

I want to see photos of the back of the carpet, the padding, and of the subfloor below the padding.

That will tell us for sure if there as been a water leak or some other leak, in which case we'll want to track the leak to its source before proceeding with new flooring.

On 2020-05-13 by Lori

Thank Dan. When the flooring guy gets here, we will do just that!

Reply by (mod) -

Excellent

Take photos, let me know what you see, and we'll take it from there.

 

On 2020-04-19 by Cj - what are these greenish black spots on my wall to wall carpet

My carpet has these spots that have been slowly growing over time. I clean it and it just comes back, there is a ceiling fan and a tenant that lives below me. It did appear to feel a little moist.

Do you have any idea of what it could be?

Reply by (mod)

CJ

Sorry, no. Not without more investigation.

Does the area smell moldy if you sniff close to it?

Could you pull back the carpeting from the wall so as to allow an inspection of its underside as well as the condition of the padding below and the subfloor below that?

That inspection would tell us if this is a recurrent stain from a spill or if instead it's moisture from a leak below.

On 2019-12-23 by Soph - what caused this dark reddish brown carpet stain that is getting bigger

Hello I’ve noticed this random patch which has gradually gotten bigger and darker in colour over the months

Can anyone tell me what it? The boiler is in a cupboard to the right of the patch about a meter and above the patch is french windows that lead to the garden
Thank you

Reply by (mod) -

I'd start by looking for something like an active leak near or above that brown spot to see if there's a drip or was a drip such as from a window air conditioner or wind-blown rain or snow-melt leaks at the French doors themselves.

On 2019-12-23 by Soph

There’s just floorboards underneath the carpet It’s just very strange it’s in the middle like that

Reply by (mod) -

Agree; usually such a stain is from above - a spill or drip; sometimes such stains "grow" over time due to bacterial action or even simply migration of the staining agent through the fibers. Or due to additional drips or spills (or burns etc) onto the spot.

On 2019-12-23 by Soph

But the stain has disappeared in the past, when I’ve had the carpet professionally cleaned the stain will lighten and You won’t be able to tell it’s there. But now it seems it’s back with a vengeance.

When you say “above” what do you mean?

The only thing above would be the ceiling and there is nothing coming down from the ceiling onto that spot.
Could it be that the doors to the garden are nearby ?!

Reply by Mod

I mean any water or other liquid source that could drip onto the carpet in the area of that stain

or

A leak or water source nearby that might leak towards that spot from under the carpet

So: pulling up the carpet to see the condition of the floor below will tell us if the leak comes from below or above.

 

On 2019-12-02 by Gale

Big patches of light colored stains are appearing randomly on my carpet. The carpet has been down about 8-10 years and this has just started happening.

The carpet is a soft gold, beige color. These stains are mainly in the dinning and great room. We have gas logs in our great room. They are now beginning to appear in our bedroom (same carpet). The carpet has never been wet.

Reply by (mod) - light areas on carpet - prior cleaning efforts?

Looks like areas where the carpet was previously cleaned of spills or stains.

On 2020-10-13 by Kirsten

Hi, id like to know if there was an outcome to post on 2019-12-02 by Gale.

Those marks arw on a carpet we extraction cleaned 8 months ago and they are getting larger and also appear elsewhere in this house near ac vents in the floor (same colour, just not splotchy looking like the other areas throughout the house.

Reply by (mod) -

Kirsten

I did not hear further from Gale, but in general, when I see sharply-delineated areas on a carpet that are lighter than the surrounding space I think that the most common causes are

- efforts to clean up a prior spill or stain (these usually have somewhat indistinct edges

- a spill of a liquid that actually bleaches out the carpeting (these usually have sharp edges)

Those include liquids like (and NOT necessarily RECOMMENDED for carpet cleaning) dilutions of ammonia, bleach, lemon juice, laundry detergents, vinegar

After using a humidifier for a couple months I noticed stains on carpet underneath nightstand where humidifier is.

Do I have mold? - On 2019-10-24 0 by Frida

Reply by (mod) -

Quite possibly if your humidifier leaked or caused condensation or water acuumulation anywhere indoors.

Was the carpet indeed wet - ever?

What caused these blue and small brown rust stains on my carpet?

What may cause this on my carpet it’s in my bedroom also - On 2019-09-16 by Mary -

Reply by (mod) -

Mary I see two discolorations, a darker area along the carpet close to the wall which sometimes is caused by an air leak (those are usually dark gray or black, and would be continuous along the wall)

Your stains look blusih and discontinous, but that could also have been left if someone tried using a cleaning liquid in this location.

Those small reddish stains that could be from a spill or from rust marks on carpet under metal furniture casters used on damp or wet carpet.

Was there previously furniture or some other fixture placed in this location?

...

Continue reading at CARPET STAIN ID TESTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see CARPET STAIN DIAGNOSIS FAQs - questions & answers about stained carpets & rugs, posted originally at this page.

Or see these

Recommended Articles

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  • CARPET TACK STRIPS & FLOODS
• CARPETING & INDOOR AIR QUALITY
• CARPETING, SELECTION & INSTALLATION
• DUST SAMPLING PROCEDURE
• FIRST AID for PET-PEED-ON CARPETS & FLOORS
• SEWAGE CLEANUP PROCEDURES & STANDARDS - don't try to clean sewage-contaminated carpets 
• SMELL PATCH TEST to FIND ODOR SOURCE
• STAINS on INDOOR SURFACES, PHOTO GUIDE

Suggested citation for this web page

CARPET STAIN DIAGNOSIS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STAINS

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Or see

INDEX to RELATED ARTICLES: ARTICLE INDEX to ANIMAL PESTS, ALLERGENS, HAZARDS

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Citations & References

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