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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
AIR CLEANER PURIFIER TYPES
AIR POLLUTANTS, COMMON INDOOR
AIR QUALITY IMPROVEMENT STRATEGIES
AIRBORNE PARTICLE ANALYSIS METHODS
ALLERGEN TESTS for BUILDINGS
ASBESTOS IDENTIFICATION IN BUILDINGS
BACKDRAFTING HEATING EQUIPMENT
BLACK MOLD, TOXIC & ALLERGENIC
BLEACHING MOLD, Advice about
BOOKSTORE - ENVIRONMENTAL
CADMIUM in the HOME
CARBON MONOXIDE - CO
CARPETING & INDOOR AIR QUALITY
CAT DANDER in BUILDINGS
CELL PHONE RADIATION
CHEMICAL CONTAMINANTS in WATER
COMBUSTION PRODUCTS & IAQ
DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS
DUST SAMPLING PROCEDURE
EMERGENCY RESPONSE, IAQ, GAS, MOLD
EMF ELECTROMAGNETIC FIELDSRE
ENDOCRINE DISRUPTERS at BUILDINGS
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR TILE ASBESTOS IDENTIFICATION
FUNGICIDAL SPRAY & SEALANT USE
GAS EXPOSURE EFFECTS, TOXIC
HEATING OIL EXPOSURE HAZARDS, LIMITS
HOUSE DUST ANALYSIS
HOUSE DUST COMPONENTS
HUMIDITY CONTROL & TARGETS INDOORS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
LAB PROCEDURES MICROSCOPE TECHNIQUES
LEAD POISONING HAZARDS GUIDE
LEGIONELLA LEGIONNAIRES' DISEASE
LIGHT, GUIDE to FORENSIC USE
METHANE GAS SOURCES
MILDEW in BUILDINGS ?
MOISTURE CONTROL in BUILDINGS
MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
MOLD CONSULTANTS / INSPECTORS
MOLD DETECTION & INSPECTION GUIDE
MOLD EXPERT, WHEN TO HIRE
MOLD RELATED ILLNESS GUIDE
MSDS MATERIAL SAFETY DATA SHEETS
MVOCs & MOLDY MUSTY ODORS
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
OIL, HEATING, EXPOSURE HAZARDS, LIMITS
OIL HEAT ODORS & NOISES
OIL SPILL CLEANUP / PREVENTION
PET ALLERGENS / PET DANDER
PET STAINS & MARKS in BUILDINGS
PLASTIC ODORS-SCREENS, SIDING
PLUMBING SYSTEM ODORS
PVC - VINYL BUILDING PRODUCTS
RADON HAZARD TESTS & MITIGATION
SAFETY HAZARDS GUIDE
SAFETY HAZARDS & INSPECTIONS
METHANE GAS HAZARDS
SEPTIC SYSTEM ODORS
SEWAGE BACKUP TEST & CLEANUP
SEWER GAS ODORS
SMELL PATCH TEST to Track Down Odors
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
SULPHUR & SEWER GAS SMELL SOURCES
UFFI UREA FORMALDEHYDE FOAM INSULATION
URETHANE FOAM Deterioration, Outgassing
VINYL CHLORIDE HEALTH INFO
VOCs VOLATILE ORGANIC COMPOUNDS
WATER ODORS, CAUSE CURE
WORLD TRADE CENTER 9-11 DUST PHOTOS
Composition of house dust or building dust: this article describes the common as well as less-common constituents of house dust and typical office building dust. We also cite the occurrence of particles that may indicate indoor air quality concerns, hazardous conditions, or other building conditions that may be detected or perhaps simply suggested by the presence of certain particles in air, in settled building dust, or in vacuum-cleaner collected or clothes dryer-collected dust and lint.
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Typical components of house dust and typical office building dust are dominated by fabric fibers and skin cells. Common too are lower levels of dust mite fecals, insect fragments, and air-delivered pollen and mold, though the levels of these varies seasonally and by changes in the indoor environment such as in humidity.
At above left our photo illustrates house dust containing fabric fibers, starch granules (upper center), skin cells (left), and probable soil-particles. In a wet building skin cells and animal dander may also show secondary bacterial growth. At above right is an example of animal hair (cat) commonly found indoors, even in homes where no pets are currently living.
Normal Levels of House Dust are OK
Cat allergens (cat dander) are common and are often more allergenic to building occupants (ALLERGENS in BUILDINGS) than dog dander or animal hair in general.
Our page top photo of typical "dust bunnies" that collect on building floors below furniture and under radiators, and our photo of a dusty table top (at left) are fairly normal of an indoor building prior to typical houscleaning vacuuming and dusting operations.
Watch out: dust is a common and normal material found in almost all buildings. Only in controlled environments such as computer chip manufacturing lines do we expect to find few airborne particles.
Do not seek an objective of "no indoor dust" in a normal building: doing so wastes money and time and is not rational.
Abnormal Levels of House Dust May Not be Acceptable
Our photo at left shows a very dusty indoor surface characteristic of poor housekeeping.
Even if this dust contains only typical house dust components the dust level is likely to be irritating to some people (including the author) who are asthmatic or have allergies.
So how do we decide between just cleaning up obvious dust and debris indoors and the need to hire a building expert to look for hidden contaminants and if found to write a building remediation plan?
At MOLD EXPERT, WHEN TO HIRE we give a rational to help decide when further investigation of the indoor envrionment appears warranted.
Abnormal Indoor Particles Can Indicate Indoor Air Quality Problems or Health Hazards
We may however find either higher levels of common problem particles (allergens, insect fragments, mold, fiberglass or other insulation fragments) or low levels of particles that by their nature (such as Aspergillus sp. mold spores in chains) still indicate a problem.
Or we may find abnormal and possibly harmful levels of asbestos, concrete or silica, small fiberglass fragments, lead dust, mold at high levels, oil burner or fireplace soot, or non-particulate hazards such as gases or chemicals that are not addressed here.
Our photo at above left illustrates a dust mite head fragment. At above right is a cockroach insect jaw fragment. More often we see insect hairs, wing fragments, and fecal pellets.
While dust mite fecals are common in house dust, higher levels of actual insect fragments may indicate higher indoor humidity, or the presence of extra levels of mite sources (animals, animal dander, poor housekeeping). ( HUMIDITY CONTROL & TARGETS INDOORS.)
Fergusson et al (1986) point out that heavy metals may also be present in dust samples. (Also see LEAD POISONING HAZARDS GUIDE)
Still other biological hazards can be present such as bacteria and viruses. And particularly for buildings near highways, active streets, construction or demolition projects, tire particles, road dust, and CONCRETE DUST & ODORS can be significant ingredients in indoor air and in building or house dust.
All of these may appear at harmless, harmful, or suggestive levels in building dust or other indoor environmental samples.
In addition to our example data and photographs, this article includes citations to authoritative research on the components of house dust, building dust, vacuum-cleaner dust, and clothes dryer dust.
At above left we illustrate a microscopic close-up of dog hair, in this case from a golden retriever. The photo at above right illustrates a mix of skin cells (larger fragments) and dog dander heavily stained with acid fuchsin. Normally these particles are hyaline (colorless).
We may find examples of mouse or rat hair at levels suggesting a rodent infestation problem. In some areas rodent infestation is of course also associated with other diseases ranging from Hantavirus to plague.
The dust mite fecals in our photo at below left along with the background of this picture give important building diagnostics.
The fecal pellets themselves are comprised largely of mold spores, and in the background (not in focus) are spore chains that are most likely Aspergillus sp. or Penicillium sp.
While it is normal to find mold spores in both outdoor and indoor air ("all mold is everywhere all the time - it's just the concentration that varies" - Haines), observing mold spores that dominate the sample by frequency or even at low levels in chains is likely to indicate a mold contamination reservoir in the structure where this sample was collected. (CONCENTRATION BURSTS of Mold Spores)
Finding particle in connected chains - in this case both the fecal pellets and the Pen/Asp spores - often indicates a contemporary and nearby contaminant source. Why? Because normally in transport through air these chains are quickly broken apart into individual particles.
Watch out: We do not recommend that every building be screened for mold nor other problem particles. But when conditions warrant, further investigation is appropriate. (MOLD EXPERT, WHEN TO HIRE).
There may be other less-expected contaminants in building dust. For example, following a sewage flood or septic back-up in a building, both bacterial and viral hazards may be attached to common house dust particles (SEWAGE CONTAMINATION inBUILDINGS).
While an initial inspection did not show structural damage to the wood framed home where this sample was collected, I saw some yellowish "dust" under a kitchen sink cabinet and on nearby sills. In the lab it was quickly apparent that we were looking at spores of Meruliporia incrassata or "poria" referred to by those who prefer scarier terms as "the house eating fungus".
We don't normally find this particle in buildings unless there is a rot problem. Further investigation of the building floor framing and sills found extensive rot damage that had not at first been apparent. (MERULIPORIA FUNGUS DAMAGE)
And the collapse of the world trade center demonstrated (World Trade Center Collapse Dust) that in extreme conditions, for which more normal building remodeling or demolition are surely examples, dangerous levels of asbestos, lead, other metals, may be present in the building air and dust.
Magnified to 720x dust particle fibers found in a healthy building are primarily cotton, wool, with some linen and a synthetic fabric fibers. Depending on the presence of carpeting the fiber mix will vary according to the carpet or other furnishings.
At left and in the photo at page top we illustrate simple settled dust on indoor horizontal surfaces. For building particle screening I like settled dust samples even though simple quantitative analysis cannot be performed.
By observing what particles are dominant in such a sample and by watching out for unusual particles that still form contamination clues we can get a good idea of what particles are actually indoors. At the same time we steer clear of the serious errors that plague highly precise but grossly -inaccurate air particle testing. (ACCURACY vs PRECISION of MEASUREMENTS and AIRBORNE MOLD COUNT VALIDITY)
Watch out: While "air tests" or air sampling methods for particle collection are popular with many building investigators (quick, easy, profitable), such tests, when not accompanied by an intelligent inspection of the building exterior and interior along with a taking of building history, components, and occupant complaints, is simply not reliable, especially if results appear "negative" (FALSE NEGATIVE Results in Mold Tests). I elaborate this opinion at AIRBORNE MOLD SPORE COUNT ACCURACY.
Above (left) we show a 720x micro-photograph of white blown-in un bonded InsulSafe® building insulation sold by CertainTeed. At above right our photo shows the dominant particles in the dust sample from the home under study.
For instructions on how to collect surface dust for lab analysis, see DUST SAMPLING PROCEDURE where we also discuss finding mold in indoor dust samples. Readers concerned with fiberglass in building dust (discussed here) should also see FIBERGLASS HAZARDS.
At DUST SAMPLE TYPES we distinguish between "old house dust" and "recent house dust" which in turn can aid in building indoor air quality investigation diagnosis.
House Dust Component Studies, References, Citations
Common toxins, pathogens, or allergens in house dust.
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Frequently Asked Questions (FAQs)
Question: how to proceed in solving a bothersome indoor air quality and dust problem
2/19/2014 Karen said:
I found all of your articles to be very professional, forthright, and informative. I have been experiencing some air quality problems in my home.
To the extent that I have developed a severe allergic reaction every time the heat or air condition is on. We had a mold inspection and testing done and the results were negative. Although this was good news the problem persists. I've also discovered black soot on the glass surfaces, an unusually extreme amount of black fiber like particles on surfaces, along with a cottony like dust on services as well.
We also had the air ducts cleaned to try to rectify the problem but this also did not resolve the issues. I purchased an air purifier which collects the black particle and dust on a daily bases. The particles have also settled on our clothing in the closets.
Finally, there is black soot like substance on the carpet edges against the walls in the bedrooms. The rest of the house has hardwood floors. I'm suspecting that it could be fiberglass particles being released through the HVAC systems and/or the insulation has been infiltrated by mold. - K. 2/19/2014
Karen, thanks for the nice comment about our website: we work hard to provide authoritative and unbiased information so I'm always thrilled when someone reports finding our work useful.
Now to the question: without more information about the building, its condition, history, occupant complaints, and absent a smoking gun observation of a significant mold contamination problem, and without an observation of mold odors, I would not start by assuming we are looking at a mold problem.
I would take a careful look at the building and its mechanical systems and at occupant complaints, focused on identifying the highest risk areas that may justify further testing or even invasive inspection if that's appropriate. MOLD EXPERT, WHEN TO HIRE has some advice about how we decide if hiring an expert is appropriate compared with a DIY approach or using building cleaning or maintenance contractors or a home inspector to take a look for you.
1. I would not assume that a mold "test" alone would be reliable - with all test methods there is a high risk of false negative results; if your "mold inspection" was by someone who understands buildings, where leaks and water go, where mold grows, etc. that would be most helpful.
2. The HVAC system could have a mold or other respiratory irritant reservoir in the air handler or duct system, but it can also simply be moving air from one building are to another, moving irritants in the process. Pay particular attention to where return air is being picked up.
3. Without more data I would not assume the issue is mold, though if you say the building history includes leak or moisture traps that'd be a reasonable concern.
4. The debris depositing you describe can be easily tested (see our DIY house dust test kit procedure using adhesive tape) and with a competent environmental lab should be inexpensive - sometimes the dust or debris contains something unusual that points to a problem source.
5. Black stains around carpet edges suggests air leakage to me - suggesting air moving up from the space below. If your hone includes a crawl space that's an area deserving careful inspection.
6. Air purifiers: regarding your lack of success trying to address these concerns with a portable air purifier, IMO there is no portable air purifier or more accurately air cleaning machine on the market, nor has there been, nor is there likely to be, that is capable of removing an IAQ problem source in a building any more than you could vacuum dust bunnies from under the living room couch by waving a vacuum cleaner wand in the air in the kitchen. Perhaps in a small, enclosed space that does not itself contain the problem reservoir a portable air filtration device or well-designed central air handling system filtration can reduce the airborne particle level but that's not going to correct the underlying problem.
Questions & answers or comments about fiberglass dust particle identification procedures & testing.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
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