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fibers not fiberglass (C) Daniel Friedman Composition of Building Dust or House Dust
Particle Types, Hazards, Identification

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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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What are the Contents of House Dust & Office Building Dust

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.

fibers not fiberglass (C) Daniel Friedman

At above our photo illustrates house dust containing fabric fibers, starch granules (upper center), skin cells (left), and probable soil-particles.

fibers not fiberglass (C) Daniel Friedman

In a wet building skin cells and animal dander may also show secondary bacterial growth. Above 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

fibers not fiberglass (C) Daniel Friedman

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

Very dusty indoor surface (C) Daniel Friedman

But abnormal levels of certain particles in building air or dust can indeed indicate an indoor air quality or indoor environmental problem that needs to be addressed.

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 / ENVIRONMENTAL EXPERT, 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.

Dust  mite fragment (C) Daniel Friedman

Our photo at above left illustrates a dust mite head fragment.

Dust  mite fragment (C) Daniel Friedman

Above 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).

See 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.

Dog dander allergens (C) Daniel Friedman

At above left we illustrate a microscopic close-up of dog hair, in this case from a golden retriever.

Dog dander allergens (C) Daniel Friedman

The photo above illustrates a mix of skin cells (larger fragments) and dog dander heavily stained with acid fuchsin. Normally these particles are hyaline (colorless).

Mouse hair (C) Daniel Friedman

Examining animal hair samples in a building may be diagnostic for a different reason.

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.

Dust mite or other insect fecals (C) Daniel Friedman

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.
See 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.

See MOLD / ENVIRONMENTAL EXPERT, 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.
See SEWAGE CONTAMINATION in BUILDINGS

Meruliporia fungal spores - house eating rot fungus (C) Daniel Friedmanb

An interesting example of a surprise particle found in building dust is shown in our photo at left.

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.

Flashlight dust (C) D Friedman

Separate studies, especially by industrial hygienists, document airborne dust, chemical, or gaseous hazards more common in industrial buildings & complexes both indoors and outside.

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.
See 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.

Fiberglass Fibers vs Fabric Fibers in House Dust

Certainteed blown in fiberglass (C) Daniel Friedman fibers not fiberglass (C) Daniel Friedman

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.

Typically we collect dust from building surfaces using clear adhesive tape (MOLD TEST KITS) or vacuum cassetts (VACUUM CASSETTE FILTER SAMPLE).

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.

Other useful citations on the ingredients of house dust are given at CONCRETE DUST & ODORS and at LEAD in AIR, EMISSIONS STANDARDS and LEAD POISONING HAZARDS GUIDE

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Continue reading at DUST SAMPLE TYPES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see HOUSE DUST PARTICLE PHOTOS - a photo tour of what we found in dust from a London loft.

Or see HVAC DUST CONTAMINATION STUDY - what do we find in dust in a heating or air conditioning system?

Or see DUST SAMPLING PROCEDURE where we also discuss finding mold in indoor dust samples

Suggested citation for this web page

HOUSE DUST COMPONENTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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