Photograph of chopped fiberglass insulation Airborne Fiberglass & Fiberglass Dust Hazards in buildings

  • FIBERGLASS FRAGMENT HAZARDS in AIR or DUST - CONTENTS: Possible concerns of airborne and dust-borne fiberglass fragments in buildings.
  • POST a QUESTION or READ FAQs about fiberglass contamination indoors: what is the role of particle size in the detection of airborne fiberglass in dust samples? What is the role of particle size in health hazards from airborne fiberglass or other particulates?
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Airborne fiberglass dust hazards & the role of particle size in particle detection as well as in health risk assessment:

Most buildings Probably have Mostly Large Fiberglass Fragments. Prudent Avoidance of Fiberglass Insulation Dust makes sense.

This article provides information about fiberglass fragments and indoor air quality fiberglass contamination issues in residential and light-commercial buildings.

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Airborne Fiberglass Fragments as a Possible Health Concern

Home made return duct using fiberglass insulation (C) Daniel FriedmanA Guide to Large versus Very Small Fiberglass Fragments in Building Dust

In our page top photo of fiberglass insulation fragments collected in an indoor air sample, you can see not only a large and typical fiberglass insulation strand with its characteristic colored resin binder. You can also spot much smaller fiberglass fragments.

When a forensic laboratory is asked to screen dust or air samples for fiberglass, depending on the lab's protocols it's not certain that fibers of both large dimension and small fiber fragments will both be reported.

Small glass fiber fragments are easily "lost" in other non-fungal granular debris in building dust. We posit that studies of the level of airborne fiberglass in buildings may be faulty if the methods used to screen for fiberglass fragments do not include small, even sub-micron particles along with the common large particles.

Most buildings Probably have Mostly Large Fiberglass Fragments - Some Have Sub-Micron Fragments of Fiberglass Dust

Our field and lab experience suggest that while we find fiberglass in nearly all modern indoor environmental dust, the common particles are usually long and large (and presumed less of a health risk than very small particles).

However in environments where fiberglass insulation is old, damaged [photo] by foot traffic, handling, pests such as mice, or where it was chopped or disturbed, on occasion we find high levels of very small, even sub-micron fiberglass particles.

We may also find an elevated level of small fiberglass insulation fragments in buildings or in the HVAC system of buildings where fiberglass-lined HVAC ductwork has been mechanically cleaned [photo] - a process that can loosen and damage the fiberglass liner.

We have also found high levels of fiberglass fragments in indoor air and dust in buildings where amateur do-it-yourself return air ducts were constructed using conventional fiberglass insulating batts as a "duct" liner (photo, above-left).

Therefore a first level of inspection for this hazard starts with the age of the building and the visual determination of the condition of its insulation.

photo of resin binder on fiberglass insulation fibers

Fiberglass fragments are inorganic material typically from fiberglass insulation; depending on their size and quantity these may be a respiratory irritant or may contribute to more serious health concerns.

The presence of incidental occurrence of fiberglass fragments and fibers in buildings is common.

The Association of Man-made Mineral Fiber Producers asserted to the US EPA in 1992 that a study at that time " does not provide evidence of significant adverse health effects following inhalation of glass fiber."

("Respirable Fibrous Glass Chronic Multidose Inhalation Study-Preliminary Final Results," TIMA, 4 May 1992 delivered to U.S. EPA by hand.) The Seventh Annual Report on Carcinogens (June 1994) lists glass fibers of respirable size as a substance "reasonably anticipated to cause cancer in humans."

DJF Opinion: Caution about fiberglass fragment size: when reading studies about airborne fiberglass, pay close attention to the methods used to collect samples and the methods used to identify and count fiberglass particle fragments.

For example, some counting devices or microscopic methods exclude all particles below a give size by the choice of instrument or counting method itself.


Deciding not to look for very small particles (which if present may be the more harmful ones) or using a methodology that excludes them means that study is not going to find them even if they in fact were dominant by number or even total volume in a sample.

photo of glass wool insulation

Prudent Avoidance of 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. It seems reasonable to me to suggest that that prudent avoidance of fiberglass dust would be appropriate.

Improper cleaning or treatment of fiberglass ducts with biocides and particularly, mechanical cleaning that can damage the fiberglass lining HVAC ducts may in fact increase rather than decrease indoor air quality problems in a building, particularly if occupants have other respiratory or pulmonary concerns/vulnerabilities.

See Glass Wool Fibers Expert Panel Report, Part B - Recommendation for Listing Status for Glass Wool Fibers and Scientific Justification for the Recommendation" [PDF] for a 2009 update on the carcinogenicity of fiberglass fragments.

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.

Reader Question: exposure to airborne fiberglass & VOCs from fiberglass boat manufacture

19 March 2015 Anonymous said:

I have a related question as well, i work in a an area where we are on a second floor and on our ground floor, is our production area, wherein the polish a fiber glass boat. My concern is when our AC is open, Is the fiber being suck up by our AC wherein we get to inhale the fiber? At the same time, we can even smell the resin, is this dangerous to our health??

Reply: OSHA Workplace Safety Forms


This is an OSHA workplace safety question for you and your company's safety officer, and in my OPINION a valid one, and not one for which the actual risks can be assessed by an e-text. Rather an onsite inspection by an expert would be needed.

If you need help from OSHA and the U.S. Department of Labor, see:

While no one can assess risks in your workplace by just a text inquiry, it is reasonble to say that it is possible for particles and gases to be transported from one building area to another by an HVAC system, more-so if its filtration is not designed for the tansk at hand. Odors from resins or chemicals used in making a fiberglass boat (styrene emissions) or for cleaning up (acetone) are quite volatile - it's no surprise that they'd spread in a building. These hazards have been investigated by experts. For example, see


Continue reading at FIBERGLASS HVAC DUCTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see FIBERGLASS HAZARDS in AIR or DUST FAQs - questions & answers posted originally at this article


Or see FIBERGLASS REINFORCED PLASTICS - Fiberglass Reinforced Plastics FRP - Handling, Repair & Hazard Information

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FIBERGLASS FRAGMENT HAZARDS in AIR or DUST at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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