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Air filters & airborne fiberglass: this article discusses HVAC system air filters as a potential source of airborne fiberglass versus the role of air filters as a means of removing fiberglass or other particles from indoor air: We describe a shortcoming of some field and lab investigations for airborne fiberglass: failure to sample or test for very small particles. This website answers almost any question you might ask about air filters for heating or air conditioning systems.We explain how an air conditioning service technician will diagnose certain common air conditioning system failures or defects. Readers should also see Air Filter Effectiveness and Real-World Effectiveness of Air Cleaners in our INDOOR AIR QUALITY IMPROVEMENT GUIDE article series. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Air Filters and Fiberglass Contamination in Indoor AirAir filters and their contribution to fiberglass fragments found in building air and dust
The contribution of an air conditioning or heating furnace air filter fiberglass to the overall level of airborne or dust-borne fiberglass particles in a building is likely to be insignificant, probably below the limits of detection by other than the most rigorous means, and certainly in most buildings will be insignificant compared with the contribution of other fiberglass sources such as building insulation in unprotected ceilings or walls. In fact most fiberglass that we find in building air and dust seems to originate in building insulation, especially where there is traffic or air movement in and out of areas where fiberglass insulation is exposed, and more so if that insulation is mechanically damaged such as by being walked-on. A second source of fiberglass particles in buildings is from damaged fiberglass-lined HVAC ductwork, such as ducts that use an internal fiberglass liner that was damaged by an inept attempt at mechanical cleaning.
Our photo (left) illustrates the variation in fiberglass fiber diameter as well as resin color and deposition patterns. We describe this variation further below. Fiberglass fiber metric consistency and the color of fiberglass binders are often sufficiently distinct to permit positive identification of the source of fiberglass fragments in the building environment. (See our article on laboratory identification of fiberglass found at More Information.
HVAC Air Filters Are More Likely to Reduce than Increase the Indoor Airborne Fiberglass Particle LevelIn sum, it is very doubtful that a fiberglass-based HVAC air filter is a meaningful contributor to the total load of airborne fiberglass particles in a building. There are simply too many enormously larger fiberglass particle sources that overwhelm the measurement. Any air filter, properly selected and installed and maintained, will be expected to reduce the overall level of airborne particles, including fiberglass fragments which are contributed to the building air and dust from other building sources. Do field investigators, hygienists, IAQ specialists or test labs see or even look for very small fiberglass insulation fragments?
A reasonable conclusion from these observations about the presence and difficulty in seeing small airborne particles below 10u and especially below 3u is that the better we filter the air the less we need to worry about them. Variations in fiber size in air conditioning and heating air filters
One of our clients wrote that her fiberglass-based air conditioning and heating air filters were described by their manufacturer as using fibers of 20-27u (in fiber diameter). The maker promises the filters do not shed fiberglass fragments and that the fibers are too big in micron size to become repairable even if they do shed. Laboratory examination of a filter sample sent by the client to an independent microscopy laboratory found that the filter fibers were 31 microns in diameter, and had a blue coating on them [probably the binder, and not the fragments shown in our photos here.]. The binder coating increases the effective fiber diameter. These measurements of fiberglass fiber diameters were within a normal range of variation in product manufacture that we've seen in own forensic laboratory. For example, a fiberglass fiber can break so as to release several sub-micron glass fragments - as we illustrated in our fiberglass fragment photo earlier on this page and in the additional fiberglass fragment photograph at left. This ultra-small (1-5 micron range) fiberglass fragment photo is a digital enlargement of a photograph we took at 1,900x, close to the practical limits of transmitted or reflected light microscopy. The actual filtering efficiency of an air filter should not be estimated simply on fiber diameter since more than diameter goes into the filter design, including fiber placement, randomness, average remaining opening diameter, total filter thickness, electrostatic properties of the filter, and other variables such as whether or not the filter has a gasket or is bypassing lots of air around the filter itself. Frequently Asked Questions (FAQs)No FAQs have beenn posted for this topic. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia. Ask a Question or Search InspectApediaQuestions & answers or comments about reader questions concerning fiberglass particle shedding by air filters, about labs and investigators who may fail to accurately test for small fiberglass fragments, and the variations in fiber size in different HVAC filters. . Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one. Click to Show or Hide Citations & References
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