Basement dust sample © D Friedman at Guide to Collecting a Dust or Particle Sample for Lab Analysis and Report

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Dust collection, sampling & testing to screen for hazardous dust particles:

This article describes a simple, inexpensive strategy for collecting a small number of settled dust samples in a building in order to screen for problem particles or to identify the contents of house dust. We discuss when dust sample collection and testing is justified, proper sampling & collection methods, and what to expect from a dust analysis test.

Typical components of house dust are dominated by fabric fibers and skin cells, but using dust sampling (or less reliably, airborne particle sampling) we may find high levels of problem particles (mold, allergens, fiberglass) or low levels of particles that nevertheless indicate an indoor air quality problem (such as certain mold spore genera/species found in spore chains).

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Building Dust Collection Methods: A Simple Approach

Dust sample using simple adhesvive tape and a clean plastic bag © D Friedman at

This article explains how to choose a dust sampling location and when to collect samples. Our page top photo shows a microscope photo of an interesting sample of dust from the basement of a one family home.

[Click to enlarge any image]

Typical contents include skin cells and fabric fibers, occasional dust mite fecals. But (click to enlarge) this sample also detected a significant number of mold spores (amerospores) that were identified Penicillium or Aspergillus.

Article Contents

Should we be testing for problem dust articles at all?

Probably not: If your question is simply about mold identification, and you already see mold on indoor surfaces, NO mold testing is needed to just to confirm that mold is present in the building and that cleanup is needed. Sure, it might be just cosmetic mold but for small mold cleanup jobs testing is not normally appropriate.

Maybe yes: But if you need to identify the contents of dust, for example to help track down possible sources of building dust particles, or to screen for problem particles such as dust mite fecals, insect fragments, animal dander or hair, soot, fiberglass, etc., or if a large mold remediation project is planned, tests may be needed for project control.

See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for a discussion of when it is or is not appropriate, justified, and ethical to hire an environmental consultant to inspect, diagnose, and advise about mold or other contamination in a building.

More About our Page Top Dust Sample Lab Photo

Here is what our client told us about this tape sample of basement dust:

Tape sample of settled dust in a basement after the basement was cleaned out - "this was a pretty musty basement - any cloth or paper left down there would be ruined in a short time. Sampled "before we go raising a cloud of dust in sweeping and vacuuming...40 years of dust...wife who lived in the house suffers from asthma"

It was possible that the mold reservoir - moldy basement contents - had already been removed from this basement, but the basement cleanup left lots of moldy dust on building surfaces. Additional cleaning would be appropriate. An asthma sufferer could be particularly troubled by high levels of moldy dust, or dust of almost any sort for that matter.

When, Where & How to Collect Dust Samples or Particles from a Building Surface

This expert-recommended mold test kit is easy, inexpensive, and
accurate *IF* you sample from a representative spot and *IF* you use a competent mold analysis laboratory!

If you think that problem dust is being produced in a building, then the dust source is from some active condition.That means that if you clean off a test surface and wait a sufficient time, the problem particles should appear and be detectable in a surface dust sample.

An advantage of including a dust sample from a freshly-cleaned test surface is that you can avoid confusing old dust, dirt, or debris from a prior building condition with current building conditions.

If these considerations make sense for your situation, and in order to avoid collecting and processing an unnecessarily large and costly number of dust samples, try this procedure:

  1. Choose dust sampling area: you want to collect a tape sample from a horizontal surface in the area where the dust seems worst and where the dust or other particles are most likely to be representative of building conditions being investigated. Include a sample from an area where people spend the most time.

    For details about choosing to look for old or historical building dust versus recent post-cleaning project dust,
  2. Clean off that same horizontal surface thoroughly (if we were in court I'd have you sample the cleaned surface as a control, otherwise it's not necessary)
  3. Wait a week and make a visual inspection - perhaps use a flashlight - to be sure there is dust now on the test surface. Tips on using a flashlight to examine surfaces are
  4. Collect a tape sample from that same surface in the same area.

    We explain in detail at TEST KITS for DUST, MOLD, PARTICLE TESTS how to collect and mail your own particle sample to a mold test lab. all you need is clear tape (not satin, not frosted, not invisible tape) and a plastic bag. Follow those instructions, then send your mold sample to a competent laboratory to identify the particles you found.

    In short pull off a couple of inches of clean tape, fold over on end to make a handling tab, press the tape into the sample surface, then press the tape on the outside of a clean plastic freezer bag. |
  5. Mail in the dust sample: Send just those two samples to your chosen forensic lab for analysis and comparison. In the test kit instructions just cited above we include advice about using a sample control sheet to record information about each sample if you are collecting more than one. Or use

How to Find Dust & Get the Right Dust Sample

Flashlight dust © D Friedman at

Our dust photographs at left and below demonstrate that by shining a light along a surface rather than straight at-it dust shows up very well. The very thick dust in our photo (below left) may be too much to produce a good test as it may obscure particles when we prepare a slide for microscopic examination.

That's why cleaning off a very dusty surface and following the procedure above for dust sample collection makes sense. But don't worry - in the lab we are experienced with all sorts of samples, including thick "dust bunnies". We'll be forced to pick off and throw away part of your sample in order to examine the remainder.

Our photo at below right shows that in a dark room with a bright flashlight, airborne dust can be quite obvious. More about how to use light & how to aim a flashlight to spot hard-to-see ddust or mold is at USING LIGHT TO FIND MOLD.

Flashlight dust © D Friedman at

Our photos below demonstrate further how a clean-looking indoor surface may be already rather dusty or even contain light-colored, hard-to-see mold.

Flashlight dust © D Friedman at


How Many Dust Samples Do I Need to Collect?

Flashlight dust © D Friedman at Don't let anxiety make you waste money by collecting and processing more samples than are really needed.

If the building problem you are investigating involves only a single area, or if the building problem dust appears to be everywhere in the structure, then you may still be able to select a single representative room and surface for testing.

If you need to compare conditions in different building areas, then you will need to collect dust samples that represent each area individually.

If you are testing conditions inside of a mechanical system component such as an HVAC duct interior or air handler, it will need its own samples.

If it will help, you can send the lab multiple samples but ask that the lab to process only a smaller number of them, or even just one sample. Just pay for the smaller number of samples, and ask the lab to retain the others in reserve in case further inspection is needed, or in case some of the ones you think are most likely to be representative are not productive.


Warning for people at extra risk: if there is a significant amount of mold present, or if you have allergies, suffer from asthma, have a compromised immune system, are elderly, or if infants or if others with those conditions or any other medical risk are in the building, do not attempt to collect or disturb mold. Consult your physician in any case before proceeding.

Do you need an expert? This document describes a fast, low-cost, highly-effective procedure to collect and send a "bulk" or tape mold sample to our mold testing laboratory. Sending a do-it-yourself mold test sample to a laboratory is not a substitute for consulting with or using the services of a qualified professional to inspect your building. An expert is likely to find conditions most people would not recognize.

But if you simply want to know about mold which you see yourself, the procedure below is inexpensive, scientifically sound, and easily within the ability of a typical home owner or tenant.

See MOLD TESTING METHOD VALIDITY for a discussion of the validity of various "home test kits" and "toxic mold test kits" on the market.

What about hiring someone to just do an "air test" or "swab" or "culture" for mold: You can NOT rely on air testing, settlement plates, swab testing, or culture plates to accurately and fully characterize the presence of mold in a building. Such mold test kits are unreliable and are discussed at "Test Methods Critiqued" (link at left).

While air testing and culture tests for mold can be useful tools, they are fundamentally inaccurate in characterizing mold risk in a building. Thorough visual building inspection by an experienced building scientist who is also has expertise on mold, aerobiology, and mycology, accompanied appropriate types testing of visible mold are key in any such investigation.

What Will the Forensic Lab Do With Your Dust or Particle Sample?

fibers not fiberglass (C) Daniel Friedman

On receipt of your sample the lab will prepare one or more treated slides using your material samples. We will examine them for airborne bioaerosols, mold, etc. and will perform identification using any of several low power stereoscopic and high-power light microscopes in our lab.

If the purpose of the dust analysis is to help track down its probable source in a building, the lab will identify the dominant particles in the sample including fiber type, color binder, or other particle type.

See DUST ANALYSIS for FIBERGLASS for an example.

Our lab photo (left) shows fabric fibers, starch granules (upper center), and skin cells - common ingredients found in house dust.

Mold culturing for speciation, as well as other specialized particle identification techniques are available in our laboratory and can be special-ordered by telephone or email consultation. Usually culturing is inaccurate and unnecessary as only a small percentage of organisms, mold or otherwise, will grow in a specific culture media.

Genera/species or particle identifications are made based on experience, education, reference texts and keys, and by comparison with our very extensive library of known particle samples.

While certain problem particles (including molds) are well documented and may be identifiable some are not so we do not guarantee that we will identify all components found on the tape. There are thousands of particles that appear in building dust, including more than 80,000 mold species which have been identified and an estimated 1.4 million remaining to be identified.

However it's quite possible to identify most problem building particles including the most common problematic mold species likely to be a concern in buildings.

Clients should also understand that there are multiple potential health hazards in buildings and that a client-selected remote-lab analyzed sample is absolutely not comprehensive. Other hazards may be present.

Ordinarily a written lab report will be provided within 24 hours of sample receipt. In a few cases (lab closed for cleaning, holidays, complicated samples needing more analysis) we need more time to complete the analysis.

If we recognize a dangerous material we will also notify you immediately. Our report will include an identification of particles and a statement about mold or other particle allergenicity or toxicity.

Details about environmental & forensic test lab procedures are found at TECHNICAL & LAB PROCEDURES


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 TEST KITS for DUST, MOLD, PARTICLE TESTS six simple steps to use clear adhesive tape to collect a surface sample of dust, mold, or other materials in a building.


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DUST SAMPLING PROCEDURE at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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