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What is in house dust? This article discusses analysis of building dust or house dust to trace its origins and to sort out whether or not dust problems are caused by the building HVAC system. A client called about an ongoing dispute with an HVAC contractor who had recently installed new heating and air conditioning equipment and duct work in her home. Mysterious thick "blue dust" was appearing throughout the home, reappearing soon even after vacuuming and cleaning. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Killer house dust? a case history: Mystery dust identified as cotton, ending dispute with contractor
Our photo illustrates a common finding in house dust, an occasional fungal hyphal fragment along with mostly non-fungal granular debris such as road dust particles. Usual components of house dust include skin cells and fabric fibers. Individual occurrences or infrequent occurrences of individual spores in air or dust samples are usually, but not always, insignificant. Significance may depend on the context of the investigation. For example we may find low levels of a not-normally-airborne spore such as Stachybotrys chartarum in a building after demolition and remediation during a mold cleanup job - probably not a concern. Finding the same particles in a home that has not been properly cleaned might indicate a need for a more careful investigation. While there were no serious health complaints nor people at unusual medical risk, the occupants were concerned, and believed that something in the ducts or air handlers was causing a problem.
Now about our client's dust concern, while the dispute had been going on for months, at the time of this call no one had performed a forensic examination of the dust itself. The client mailed me a representative sample of surface dust from the home. Here's one way surface dust can be easily collected and mailed. Readers should see these related articles: INDOOR AIR QUALITY IMPROVEMENT GUIDE, see ALLERGEN TESTS for buildings, see CARPET DUST IDENTIFICATION and CARPET PADDING ASBESTOS, MOLD, ODORS and CARPET TEST GUIDE and CARPETING & INDOOR AIR QUALITY and and CARPETING, SELECTION & INSTALLATION; See MOLD: A COMPLETE GUIDE TO MOLD; also see ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings. We'd be concerned about finding high levels of problematic mold spores, and I'd not like to find a lot of fiberglass in the sample either, both because it may be a health concern and because it'd argue for sloppy work by the contractor. House dust from an occupied home contains lots of stuff, usually dominated by skin cells and fibers from clothing and upholstery or carpets. Animal dander, particularly from dogs, cats, or mice, may be present at high levels too. In inner-city apartments I find lots of insect fragments as well, possibly cockroach allergens. And everybody's dust can be expected to have traces of dust mites, usually their fecal pellets. By examining the pellets I can often determine what the mites are eating, for example mold spores. Forensic Microscopy Basics for Particle & Fiber IdentificationThe dust sample was examined for homogeneity and then prepared for a look at high magnification in my lab, using both ordinary and polarized light, along with special microscope light wavelength filters, and combination of an index of refractive index mounting liquids combined Becke line analysis to measure the refractive index of particles. These methods can quickly separate out synthetic fibers such as Orlon or Nylon, as well as distinguishing typical road grit and fiberglass. Remarkably the dust sample from this West coast home was unusually clean. The sample was 90% cotton fibers, mostly blue with a few red ones included. There were incidental (not statistically significant) wool fibers present too. Skin cells were another 8% of the sample, and typical drywall dust and road dust made up the rest. The sample contained no mold spores, no fiberglass, no heating fuel combustion products, no ash, no paint droplets, in other words, it was cotton from a mostly blue fiber source. This dust source was certainly not from the heating system components. Without making a site inspection we can still offer some useful speculation: Look for something new in the home, carpets, drapes, upholstery, bedding, We would guess that mechanical disturbance like foot traffic, vacuuming, or other activity was combining with air movement from the HVAC system to spread dust around. Naturally, an investigator is a lot smarter when on-site than when speculating by telephone or email. But in any case, this was the end of arguing with the HVAC contractor who was clearly not at fault. See CARPETING & INDOOR AIR QUALITY See STAIN DIAGNOSIS on BUILDING INTERIORS and STAINS on & in BUILDINGS, CAUSES & CURES and STAINS on INDOOR SURFACES: PHOTO GUIDE as well as STAINS & Thermal Tracking. See Black stains from animals for details about pet stains on building floors (urine) and walls (various) and see Pet Stains on Walls for diagnosing stains such as the black marks left by pets on walls. Readers should also see STAINS on Indoor Surfaces: PHOTO GUIDE and for outdoor stains, see STAIN DIAGNOSIS on BUILDING EXTERIORS Frequently Asked Questions (FAQs)... Ask a Question or Search InspectApediaQuestions & answers or comments about what is commonly found in house dust 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.
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