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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.
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.
In contrast, at left we include one of our photographs of analysis of dust from the World Trade Center collapse - not from the building discussed in this article. (See WORLD TRADE CENTER 9-11 DUST PHOTOS).
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 Identification
The 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 for a broad discussion of indoor air quality concerns regarding carpeting, including chemicals, adhesives, odors, and VOCs associated with carpeting. See DUST SAMPLING PROCEDURE for help in collecting house dust or building dust samples for further analysis.
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)