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).
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Our page top photo shows a microscope photo of an interesting sample of dust from the basement of a one family home.
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.
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:
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.
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:
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".
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.
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.
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.
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 the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: part of our1970's building is being demolished & reconstructed without proper dust control. What should I do?
[Our university] is demolishing and reconstructing parts of our building build in built sometime in the 1970s. Half the building is being worked on while the other half has classrooms. In the past this has resulted in a considerable amount of dust, dirt and noise in the classrooms. What are or are there requirements for monitoring the air in the building. One time last semester, I was in that part of the building and had to breathe in the dust which actually smell like mold to me.
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with site environmental hazards and dust control, and frankly, your question is so important, especially in the setting of a school, that I want to be careful to avoid a lot of hand-waving speculation. That said, here are some things to consider:
An expert inspection should have identified hazardous materials such as lead or asbestos-containing products that would in turn have required extra care in site management and dust control. Beyond that, in my experience, a competent contractor is expected to recognize when they are encountering a suspect material, stop work, and demand testing. If tests show that special methods are needed, work stops until those are in place and are being handled by the right expert.
In very general terms, your observation that dust is leaking from work area into occupied space is a red flag that deserves careful and quick response. Even non-toxic dusts, say just plaster dust, can be severe respiratory irritants.
There is also risk that the dust that is not being controlled from spread to occupied spaces is also contaminating the HVAC systems in the building, not to mention a question that is implied concerning possible hazards to the workers themselves
I'm not expert on state or federal regulations about monitoring at schools during construction or renovation work. My impression from the standards and codes I've read is that there are more guidelines than laws - until a known hazardous, regulated material is encountered and confirmed.
Unfortunately, on some projects I've encountered, a wish to avoid extra costs sometimes leads administrators to eschew looking or testing, just plowing ahead with the job using ordinary contractors - which might be OK if the contractor is able to recognize and willing to stop when trouble is suspected. But pressure on the contractor is also great to just keep at it.
You should check with your state to ask what regulations or guidelines pertain to construction work being performed on schools. For an example of such regulations, you can take a look at New York's Department of Education regulations for facilities planning. Those include "Section 155.2 Construction and remodeling of school district facilities" that specifies:
In my OPINION, and summarizing,
You are describing a job that lacks proper dust control - placing occupants at a risk of respiratory illness and building indoor air quality complaints that could range from minor to serious.
It would be reasonable to
1. ask that proper dust control, barriers, negative air, whatever is required, be established immediately
2. ask that a qualified expert inspect the dust control measures AND collect some surface samples of settled dust for expert lab screening for the usual suspects: lead, asbestos, mold
Please do not suggest sending such samples to my lab - after our correspondence it would be inappropriate and a conflict of interest. For asbestos screening, you'd want a lab certified in NY for that purpose.
Question: indoor humidity problems
(July 26, 2012) kim said:
I have a 1954 lake house piecemealed together AT ground waterlevel, partly on clay, 80% indoor humidity, kinda like a cave inside. Partly inslab ducts now deteriorating, as is my health. What should i do? i've been researching for about 6 years now, you're the FIRST site i've seen talking about the problem!
That is a very very wet indoor home. You need to get an accurate determination of where that moisture is coming from (perhaps the in slab ducts) and fix that source as well as adding in-home dehumidification to get numbers down closer to 50% RH - else you're asking for mold problems.
As you've read, in-slab ducts can be the source of a variety of problems (I'm not sure how you went from our in-slab duct discussion to this page on dust sampling but you can search InspectApedia for in-slab ductwork.
Converting from in-slab air ducts can be costly if you have to fit the replacement ducts into or onto existing walls and ceilings. In some situations people surface mount and box in ducts as ceiling soffits; in others people go to a hybrid all or part hydronic (hot water) heat and eliminate all the ductwork - which of course is not going to work if your duct system is used for both heating and cooling.
12/5/2014 bruce bodnar said:
We have a 4 yr old home in sage creek winnipeg. We have the dark flooring and dark cupboards etc, 75% of the main floor is hardwood remainder carpeting. Since day 1 in this home my wife has had to vacuum(or mop) the floor and dust the cupboards at least twice weekly sometime 3 times. There are only 2 of us in the home, seniors, clean in appearance . In the first year I had our furnace ducts cleaned 3 times, I personally inspected them and they are still very clean. I use only the best furnace filters and change every 3 months, earlier if required. The dust I refer to is small particles and settles on top of every item in the home. Can you suggest what may be the cause. I would be much in your debt and my wife also of course.
The most common house dust ingredients are fabric fibers and skin cells. But I can't guess about what comprises the dust in a building that I've not seen and know so little about. You might want to simply send a tape sample of dust to a forensic lab to ask them to identify the dominant particles by frequency. Sometimes that will point to an apparent source such as damaged insulation in an AC duct or something else.
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