Detection & Hazards of Large vs Ultra-small Airborne Fiberglass & Fiberglass Dust Fragments in buildings
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Detection of airborne fiberglass:
How Airborne particle size effects on air quality testing: This document provides information about the role of particle size and lab procedures in the detection of small particles of fiberglass fragments and indoor air quality fiberglass contamination issues in residential and light-commercial buildings.
This article describes risks of inaccuracies in airborne fiberglass and similar particle studies if the forensic analyst fails to use procedures that can detect very small particles & fragments.
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.
Sources & Detection of Sub-Micron Sized Fiberglass Fragments in Building Air
Experienced forensic microscopists will almost certainly agree that it is very common to find fiberglass insulation fragments in indoor dust and air samples. Most often analysts recognize and identify large fiber particles - lengths considerably longer than other indoor dust analytes such as mold or pollen.
Here we will discuss: Large Non-Respirable Fiberglass Insulation Particles. Special problems with very small fiberglass fragment particles down to sub-micron size. Basic Dust Cleanup Advice for Indoor Fiberglass Fragments or other Small Particles. Prudent Avoidance Advice About Fiberglass Insulation Dust.
These comparatively large fiberglass particles are typically low enough in frequency and large enough in size that experts will agree that they are unlikely to pose a health risk to building occupants.
Indeed manufacturer MSDS sheets indicate that "There are no known health effects from the long term use or contact with non respirable
continuous filament fibers.
As manufactured, PPG glass fibers are non respirable.
fibers cannot reach the deep lung because they have a diameter of greater than 3.5 micrometers."
But what about the level of ultra-small [and respirable] fiberglass fragments that might be present in some buildings where insulation has been tramped-on, stomped about, or otherwise damaged and abused?
Kilburn (1992) found
Commercial rotary spun fibreglass used for insulating appliances appears to produce human disease that is similar to asbestosis.
Kilburn's findings were critiqued by Rossiter (1993).
In 2018 the level of exposure in normal buildings to and the hazards of such exposure to "small" fiberglass particles remain a topic of disagreement even when other studies have supported the assertion that there can be serious health hazards beyond dermatitis.
It would appear that "if you don't look for a particle, you won't find it and you won't report the particle" is a common problem with certain particles that may be present but not tested-for. That's particularly true if the mountant fluid used by the microscopist has a refractive index similar to glass (as in fiberglass) - the particles are there but they simply disappear from view under the microscope, regardless of magnification. (Fiberglass, even when you can see it in the microscope, also disappears under polarized light).
In our experience small fiberglass fragments in the 1u range may be present in a dust sample but will not be found unless the microscopist uses specific mounting media and scanning methods to detect these materials.
If a lab only notices and reports on large fiberglass fragments, unless the lab also specifically looked for very small fiberglass particles, the conclusion that no such particles were present is unreliable.
About these small fiberglass fragments, one manufacturer explains:
Chopped, crushed or severely mechanically processed fiber glass installed in a building and that has not been otherwise damaged may contain a very small amount
of respirable fibers that could reach the deep lung.
The measured airborne concentration of these respirable fibers in areas where severe processing of fiberglass occurred has been shown to be extremely low and well below the TLV.
Repeated or prolonged exposure to respirable glass fibres may cause fibrosis, lung cancer and mesothelioma. PPG fiber glass in the form supplied, [italics ours] does not
contain respirable fibers.
Possible Hazards of Intact vs. Damaged Fiberglass Insulation Particles
We agree that in proper and normal installations the assumption that intact fiberglass insulation sheds very little into the indoor environment, that the particles are large enough not to be inhaled deep into the lungs, and that at normal levels fiberglass is not likely to be hazardous to occupants.
The concern for the carcinogenicty of fiberglass is not new, and was cited by Stanton's rat study back in 1977.
A decade later McCurdy (1988) concluded:
If the potential of these fibers to cause
lung cancer is dose-related, as is the case for asbestos, then it
is likely that less risk accrues to today's workers and that the
danger to homeowners with attic insulation of synthetic mineral
fiber is negligible.
Interestingly that work cited long fibers as more-hazardous than short ones (for some vitreous fiber types) based on the observation that the body is able to break down small vitreous fiber particles.
Researchers generally agree that the most-common hazard to workers or others exposed to significant fiberglass dust is a form of dermatitis.
The microscope photo shown above, taken at relatively low magnification, perhaps 120x, shows indoor dust fragments including skin cells (pink) and also some long fiberglass fragments.
[Click to enlarge any image]
These particular fiberglass fragments are large enough to see easily.
DJF Opinion: Frequent presence of high levels fiberglass fragments in air and some dust samples, might suggest that damaged insulation inside an HVAC duct system or exposed and mechanically-damaged fiberglass insulation in the building may be contributing unwanted and potentially unsafe levels of these fibers.
Small Fiberglass Particles May Not Have Been Detected Nor Adequately Studied
However it is possible that the presence of and level of small fiberglass particles has not been adequately studied, perhaps because those particles do not normally occur in intact fiberglass materials and perhaps because, as I've argued, they go un-detected even when damaged fiberglass is present and being distributed in indoor air.
But having inspected several thousand buildings, we have certainly encountered conditions in which insulation has been installed or damaged in a manner risking an increased level of these small fragments.
Opinion: I frequently found fiberglass fragments in indoor air samples, particularly where fiberglass HVAC duct material are in a building and where fiberglass insulation has been left exposed in a living or
occupied area (such as in the ceiling above an unfinished basement being used as an office or family play area).
It is perfectly normal to find some fiberglass in most indoor air and dust samples.
But sometimes we find a notable increase in the volume or number of fiberglass fragments in air and dust samples, and we may, if we look with care, find a high frequency of ultra-small micron-level fiberglass fragments - almost always in an environment where fiberglass insulation or duct liner has been mechanically damaged.
How does this happen? If someone has attempted to mechanically "clean" HVAC duct work which
was lined with fiberglass insulation, it is likely that I'll find a higher presence of fiberglass fragments in indoor air and in settled dust.
The skin, eye, and respiratory irritant effects of exposure to fiberglass dust and particles has been widely acknowledged and appears, for example, in the MSDS for various fiberglass products. 
But in our opinion a concern regarding abnormally-high ultra-small fiberglass fragments are present.
"Abnormally high" would benefit from a quantitative definition but given the current fiberglass exposure standards focus on large particles, we don't have a definition nor an exposure level for small fiberglass fragments.
Causes of Ultra-Small Fiberglass Particles: mechanical damage to insulation
What may be the sources of these fiberglass fragments? Here are some examples:
Improperly-cleaned fiberglass-lined HVAC ducts in which mechanical means was used to "scrub" the duct interior -
see FIBERGLASS HVAC DUCTS for details.
Mechanical thrashing of cleaning equipment inside of fiberglass lined air ducts risks damaging that insulation.
In addition, routing HVAC air over or through conventional building insulation may also both contaminate that insulation with organic dust (supporting mold growth) and may pick up and transport small fragments of the material - more-so if the insulation is damaged.
Foot traffic on old building insulation in an attic - repeated walking on fiberglass insulation, loose fill or in batts, that has been placed atop of an attic floor or simply over joists (or the bottom chord of roof trusses) that support the ceiling below, can grind and damage fiberglass insulation.
Improper dust control during the blow-in process for a chopped fiberglass insulation retrofit might also be a source of small particles but we have not supporting data for that hypothesis.
Heath Risks from Small Fiberglass Fragments? Maybe.
Watch out: While the fiberglass industry does not necessarily agree these particles in homes constitute a hazard, independent studies and warnings at US government health-related websites suggest that there may be carcinogenic or respiratory health hazards from exposure to high levels of fiberglass particles in some buildings and/or work environments.
Really? The exposure level of small airborne fiberglass particles is likely to depend on
The size and actual exposure level of such particles in the building,
where the fiberglass is located
what means of transport are present (HVAC air returns, foot traffic, carrying dusty materials out of an attic into occupied space)
the exposure level of the occupants,
other factors such as the health and health vulnerabilities of building occupants
Small particles in the 2.5u and below range are easily breathed deeply into the lung where they can be hard to expel. Some studies cited the ease with which the body dissolves or handles these ultra-small particles.
Yet small particulates are considered an indoor air pollutant. Airborne particles in the PM 2.5 size range (fine particles defined as 2.5 u and smaller in diameter ) to PM 10 (coarse particles) have been identified as a air pollution and as a human health hazard.
Basic Dust Cleanup Advice for Indoor Fiberglass Fragments or other Small Particles
If we find frequent presence of fiberglass fibers in air or interior dust samples further investigation, cleaning, and particularly investigation of air handling equipment and duct systems in the building would be appropriate.
If fiberglass HVAC duct work has been installed I very often find significant fiberglass levels in interior air and dust samples.
Because these materials cannot be mechanically cleaned and because I do not
recommend encapsulant sprays, replacement could be in order.
We would not expect and do not usually find evidence of movement of significant levels of fiberglass fragments from insulated attics, nor from enclosed (finished) walls, ceilings into living areas under normal conditions.
Prudent Avoidance Advice About Fiberglass Insulation Dust
It is possible that small fiberglass particles in air may constitute a meaningful health risk (obviously depending on the overall exposure level) which has not been explored.
We suggest that that prudent avoidance would be appropriate.
Improper cleaning or treatment of fiberglass ducts with biocides may in fact increase rather than decrease indoor air quality problems in a building, particularly if occupants have other respiratory or pulmonary concerns/vulnerabilities.
Small vs Large Fiberglass Particle Hazard Research
Research of health hazards associated with fiberglass exposure have focused on specific industries such as boat building, and catastrophic events such as bombings in London that disturbed fiberglass in buildings. See REFERENCES, FIBERGLASS HAZARDS for more detailed citations.
Albrecht, Matthew A., Cameron W. Evans, and Colin L. Raston. "Green chemistry and the health implications of nanoparticles." Green chemistry 8, no. 5 (2006): 417-432.
Guo, Jie, Qunli Rao, and Zhenming Xu. "Effects of particle size of fiberglass–resin powder from PCBs on the properties and volatile behavior of phenolic molding compound." Journal of hazardous materials 175, no. 1-3 (2010): 165-171.
To answer the question, Does prolonged exposure to fibreglass adversely affect pulmonary function or produce radiographic abnormalities in human subjects? we studied workers in a midwestern appliance plant where refrigerator doors and previously entire cabinets were insulated with fibreglass sheeting and loose rotary spun fibreglass.
METHODS--Spirometry and lung volumes were measured, respiratory and occupational questionnaires were administered, and chest x-ray films were read for pneumoconiosis using International Labour Office (ILO) 1980 criteria in 284 workers with exposure of 20 years or more.
RESULTS--Expiratory flows were reduced including FEV1 (mean 90.3% of predicted (pr), FEF25-75 (85.5% pr), and FEF75-85 (76.2% pr). Forced vital capacity was significantly reduced (92.8% pr) and total lung capacity was significantly increased (109.2% pr). In white male smokers, a group large enough for comparisons, parameters of pulmonary function were reduced further in the presence of irregular opacities.
Forty three workers (15.1%) had evidence of pneumoconiosis on chest radiographs: 26 of these (9.1%), had no known exposure to asbestos and 17 (6.0%) had some exposure. The best judgement was that in 36 (13.0%), pulmonary opacities or pleural abnormalities were due to fibreglass.
CONCLUSION-- Commercial rotary spun fibreglass used for insulating appliances appears to produce human disease that is similar to asbestosis.
Kim, Seong Chan, Matthew S. Harrington, and David YH Pui. "Experimental study of nanoparticles penetration through commercial filter media." In Nanotechnology and Occupational Health, pp. 117-125. Springer, Dordrecht, 2006.
McCurdy, Stephen A. "Carcinogenicity of Synthetic Mineral Fibers." Western Journal of Medicine 148, no. 1 (1988): 75.
Stanton, Mearl F., Maxwell Layard, Andrew Tegeris, Eliza Miller, Margaret May, and Elizabeth Kent. "Carcinogenicity of fibrous glass: pleural response in the rat in relation to fiber dimension." Journal of the National Cancer Institute 58, no. 3 (1977): 587-603.
Abstract: Seventeen fibrous glasses of diverse type or dimensional distribution induced different incidences of malignant mesenchymal neoplasms when implanted in the pleurae of female Osborne-Mendel rats for periods of more than 1 year. Neoplastic response correlated well with the dimensional distribution of fibers.
Fibers less than or equal to 1.5 µ in diameter and greater than 8 µ in length yielded the highest probability of pleural sarcomas, and probability trends suggested that pleural sarcoma incidence increased with increasing lengths of fibers with diameters of less than 1.5 µ.
Morphologic observations indicated that fibers less than or equal to 8 µ in length were inactivated by phagocytosis. In fibers greater than 8 µ in length, the correlation of carcinogenicity with increasing length was difficult to explain.
Since neoplastic response to a variety of types of durable fibers, particularly asbestos fibers, was similar, our experiments reinforce the idea that the carcinogenicity of fibers depends on dimension and durability rather than physicochemical properties and emphasize that all respirable fibers be viewed with caution.
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I am preparing to install a HVAC system in my home which has no duct work. One of the contractors wants to use fiberglass duct system. I had already been told by a local energy check business that this would not be wise. Your article has confirmed that advice. Thank you. - Fiona
Fiberglass ductwork could be fine for HVAC application provided that it is foil-covered on all sides. What is impossible to clean is ductwork that leaves fiberglass exposed on the duct interior.
Question: where are details about testing & lab procedures for finding fiberglass in building air & dust?
Your headline suggested ways to detect fiberglass particles but the article never touches on it. I'd like to know how to test for it. - Bubba
Bubba, your note was helpful and we've clarified the text in several related fiberglass and dust articles. The article above focuses on the role of particle size in the detection of fiberglass in air and dust samples as well as in hazard research.
Question: We see fiberglass in our HVAC ducts and we get itchy
we live in a mobile (manufactured home) 1991 it was built. and we have fiberglass ductwork. You can see the fiberglass when you look into the floor vents. At times we get very itchy and so do our guests. When you look there is nothing you can see on our skin. Could our fiberglass be breaking down? Also, many of out guests expericence allergy symptoms when they come over. Any Ideas?? - Laura Dunne 5/1/2012
Laura, I haven't found significant fiberglass fiber release from fiberglass ductwork in buildings except in cases where some fool tried to clean the fiberglass-lined ducts mechanically. Mechanical cleaning or even aggressive brushing and vacuuming can damage the bonded surface of the ducts.
There could be of course many sources of allergy symptoms in a building: mold in the building or its HVAC system, animal dander even from prior animals or pets no longer present, insect fragments, even the introduction of unfiltered outdoor air during a period of pollen release.
A thorough visual inspection of the home including its HVAC system may be useful in the case you describe. Do not rely on testing alone as false results are just too likely.
Reader Comment: consider HVAC duct coatings to seal exposed fiberglass
My question to you is whether you have looked at coatings, such as http://www.fiberlock.com/mold/hvac.html to seal the fibers in place? Of course, as duct cleaner, we always recommend replacing fiberglass liner with a closed cell product like http://www.armacell.com/WWW/armacell/INETArmacell.nsf/
tandard/D489E388CFD3159EC12576D20065B99E? OpenDocument&Nav= 4111A0A8CA88966C8025774C005B9CCE.
However, when replacement is impossible or impractical, applying sealants/coatings to fiberglass duct board and duct liner is a valid alternative (especially in double-walled perforated duct). I don’t believe there are any cleaning methods that can always prevent damage or further deterioration to even new liner. Regardless, wouldn’t you agree that coating/sealing is better than nothing? Actually, I think the use of fiberglass in HVAC systems should be stopped.
Thanks for your great website, by the way.
CVI, ASCS, VSMR
Dusty Ducts, Inc.
1076 Corporate Park Drive
Office (800) 879-3878
Cell (434) 444-2640
Thanks for the discussion Ms Gallagher. We particularly appreciate comments or critique from readers who have expertise in the topic being discussed.
Indeed, I have considered duct coating coating products, have seen some applications of coatings as a "remedy" for damaged HVAC duct interiors and for interior surfaces that are soft, cannot be cleaned, and are contaminated with mold, allergens, even pathogens.
In general I agree with your position that for some cases a coating shoudl be considered, although it's a not completely reliable band-aid approach to a duct problem, a coating may be cost effective or may be suitable as a temporary measure pending a more costly duct replacement.
Concerns that occur to me about duct coatingsd are bases on (limited) field experience and include these:
later the duct coating falls off of the soft, unstable fiberglass surface to which it was applied, and no one knows that the fall-off has occurred; new IAQ hazards recur, worse, are ignored or not properly addressed because occupants think the duct problem was "fixed"
Some applications of spray-in duct sealants I've inspected were very uneven, and incomplete; if the ducts can't be inspected, coatings can be a hit-or-miss proposition that may help but is incomplete
Applications of coatings on in-slab ducts leave hazards of recurrent flooding, vermin, bacteria, pathogens, etc.
Question: airduct cleaning company to clean my HVAC air ducts caused damage - how to seal
(Sept 13, 2014) Lari said:
I have hired an airduct cleaning company to clean my HVAC air ducts. The company cleaned the ducts, but neglected to reseal them. I now have fine particles of fiberglass in the air of my home and on every surface. I have hired a company to reseal and then clean everything. Will this be a good enough fix?
(Oct 7, 2014) dolores vance said:
air duct company cleaned air ducts with brushes and created fiber glass blowing all through my condo. condo was heppa vacuumed but we are still feeling dust in air. poor air quality. we don't know what more to do. need advice
Indeed using mechanical duct cleaning methods inside fiberglass lined ducts can damage them. Applying a sealant should help and is about the best you can do other than replacing the damaged sections. Without inspecting your system I can't know if tat will be good enough for you or not. If the seal job cost is less than 40% (opinion) of we duct cost, I'd give it a try.
A visual inspection by an expert (see EXPERTS DIRECTORY at page top) can determine how damaged the ducts are, where, to what extent, and how much of the system needs replacement.
Other options in which I have less confidence include spray-application of a surface sealant in side the duct system.
(Dec 12, 2014) Angela said:
How do you recommend cleaning clothes and household items (bed, couches etc) that have been exposed to fiberglass particles?
Laundering, dry cleaning, sometimes 2x if contamination was heavy such as work clothes worn during an insulation job;
HEPA vacuuming furniture and interior areas.
Question: fiberglass hazard from fiberglass duct-board?
December 2014 Deborah asked
[paraphrasing] is there a fiberglass release hazard from fiberglass duct board?
Fiberglass duct insulation in normal (and good) condition is coated and fibers bonded or adhered so that you should not see any significant fiberglass release into building air. But if the duct insulation was damaged by mechanical cleaning that might indeed be a concern and may require action.
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 "Prepared Glass Fiber (Textile and Plastic), PPG Industries, Inc. Raw Material Specification" 06/26/97, rev 11/30/10, Specification Number: CO-1272, R. R. Eustace, Web search 01/03/2011, original source: PPG Technical PPG_Bulletin-Processed Fibers Specs-Revision 7.pdf
 "Fiber Glass, Continuous Filament", [including the products listed below]. PPG Material Safety Data Sheet MSDS, 2/27/2004, Web search 01/03/2011, original source: MSDS TAP Chopped Fiberglass.pdf
Chopped strand: ChopVantage®, MaxiChop®, Delta Chop®, Chopped Strands for Nonwovens
Coated Yarn: Hercuflex® Strand HF and HFO lines
Direct Draw: Hybon®, TufRov™, Innofiber™ NTY
Yarn: FiberGlass Yarn, Hybon® RCY, L.E.X.® Yarn, TEXO® Yarn
Mat: MPM 5 Chopped Strand Mat, Needled Mat for AZDEL, MatVantage II, Texo® HTM
Roving: Panel Roving for Continuous Laminating, Roving for Pultrusion/Filament Winding, Roving
for SMC, Hybon® Roving for Spray Up, Hybon® Woven Roving
 "Fibrous Glass
Material Safety Data Sheet.", GAF Materials Corporation,1361 Alps Road, Wayne, NJ 07470, Tel: 800 – 766 – 3411, MSDS # 1001,
MSDS Date: November 2008. Web search 01/03/2011, original source: Fiberglass_MSDS__1001-309-280-v1.pdf
 "Insulation Overview", Healthy House Institute, Web search 01/03/2011, original source: Insulation_ Insulation Overview - HealthyHouseInstitute.pdf, website: healthyhouseinstitute.com
 "Inspecting Attic Insulation", Washington State University, Extension Energy Program, 2006, Web search 01/03/2011, original source: AHT_Inspection Attic Insulation.pdf
Fiberglass carcinogenicity: "Glass Wool Fibers Expert Panel Report, Part B - Recommendation for Listing Status for Glass Wool Fibers and Scientific Justification for the Recommendation", The Report on Carcinogens (RoC) expert panel for glass wool fibers exposures met at the Sheraton Chapel Hill Hotel, Chapel Hill, North Carolina on June 9-10, 2009, to peer review the draft background document on glass wool fibers exposures and make a recommendation for listing status in the 12th Edition of the RoC. The National Institute of Environmental Health Sciences is one of the National Institutes of Health within the U.S. Department of Health and Human Services. The National Toxicology Program is headquartered on the NIEHS campus in Research Triangle Park, NC. The National Institute of Environmental Health Sciences is one of the National Institutes of Health within the U.S. Department of Health and Human Services. The National Toxicology Program is headquartered on the NIEHS campus in Research Triangle Park, NC.
Following a discussion of the body of knowledge, the expert panel reviewed the RoC listing criteria and made its recommendation. The expert panel recommended by a vote of 8 yes/0 no that glass wool fibers, with the exception of special fibers of concern (characterized physically below), should not be classified either as known to be a human carcinogen or reasonably anticipated to be a human carcinogen. The expert panel also recommended by a vote of 7 yes/0 no/1 abstention, based on sufficient evidence of carcinogenicity in well-conducted animal inhalation studies, that special-purpose glass fibers with the physical characteristics as follows longer, thinner, less soluble fibers (for 1 example, > 15 μm length with a kdis of < 100 ng/cm2/h) are reasonably anticipated to be a human carcinogen for the listing status in the RoC. The major considerations discussed that led the panel to its recommendation include the observations of tumors in multiple species of animals (rats and hamsters). Both inhalation and intraperitoneal routes of exposure produced tumors, although inhalation was considered more relevant for humans.
World Health Organization International Agency for Research on Cancer - IARC Monographs on the Evaluation of Carcinogenic Risks to Humans - VOL 81 Man-Made Vitreous Fibers, 2002, IARCPress, Lyon France, pi-ii-cover-isbn.qxd 06/12/02 14:15 Page i - World Health Organization, 1/21/1998. - Fiberglass insulation is an example of what IARC refers to as man made vitreous fiber - inorganic fibers made primarily from glass, rock, minerals, slag, and processed inorganic oxides. This article provides enormous detail about fiberglass and other vitreous fibers, and includes fiberglass exposure data.
http://monographs.iarc.fr/ENG/Monographs/vol81/mono81.pdf - the article (large PDF over 6MB)
http://monographs.iarc.fr/ENG/Monographs/vol81/mono81-6A.pdf - article details
http://monographs.iarc.fr/ENG/Monographs/vol81/mono81-6C.pdf - studies of cancer in experimental animals in re vitreous fibers such as fiberglass;
http://monographs.iarc.fr/ENG/Monographs/vol81/mono81-6E.pdf - summary of data reported & evaluation
http://monographs.iarc.fr/ENG/Monographs/vol81/mono81-6F.pdf for the article references
To search the IARC monographs on various environmental concerns and carcinogens, use http://monographs.iarc.fr/ENG/Monographs/PDFs/index.php
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