Sampling Dust To take a dust sample from any solid sur- face, press a short piece of transparent adhe- sive tape to the surface and then mount the tape (sticky side down) on a glass slide (or another strip of tape if a slide is not avail- able). Count and characterize (e.g., thin, round, filamentous, granular, cubic) and count visible dust particles using a 10x mag- nifier (thread count or linen tester). Since linen testers have a 1/2 × 1/2 in. (1.27 × 1.27 cm) scale plate field for counting, it is a reproducible template and therefore easy to make real-time objective comparisons before and after cleaning, or for any other parameter under study. To aid in characterizing dust on the slide, illuminate the slide with the LED white light and UV flashlights. The tape-on-microscope slides can easily be used to further charac- terize the dust using a microscope. Further characterization of dust particles can be done under white light, a polarizing filter, or polarized light and UV light. Simply characterize what you see using The Particle Atlas comparison. In taking initial samples, try to find the cleanest and dustiest place (strictly subjec- tive) to give an idea of dust–mass concentra- tion limits that can subsequently be used to develop a gradient in establishing cost-e ec- tive cleaning protocols, ventilation mainte- nance schedules, or contamination control strategies. Use an inspection mirror to locate dust accumulation on high sills and dust bunnies (yes, that is the proper term) in areas with little air movement. For simplicity after counting, set either a two-, three-, or four-point gradient of the count to illustrate strategies and establish protocols. Gradients are a good indication of air patterns and people’s movement. It will provide some ideas about the air cleaning capability of ventilation systems over time and verify where most dust is generated and hopefully, from where it comes. After further sampling, use either a stratified or random pattern for a reasonable statistical assurance of repeatability (U.S. Department of Defense, 1989). Because of ventilation and activity, dust counts should not be used to measure the eectiveness of cleaning. Rather, these counts are used to demonstrate where extra cleaning e orts are directed in developing
Photo 1. Basic field dust sampling tools. Outer circle: ATP luminometer and kit, UV flashlight, inspection mirror, and LED white light flashlight. Inner circle: Plain glass microscope slides, thread counter or linen tester, clear adhesive tape, and airflow detection powder. Photo courtesy of Dr. Robert Powitz.
pler should also provide flexibility for both continuous and intermittent operation. This feature is particularly useful in monitoring dust loading generated during construction in schools, medical facilities, and custodial care facilities. These features, in addition to allowing a correction factor that is provided by the closest U.S. Environmental Protection Agency (2023) air quality monitoring station, o er a wide range of sampling and interpre- tive options depending on the environmen- tal conditions (both activity and structural) found at the site. The second essential component is an illustrated particle atlas (McCrone et al., 1973). A good used copy can be found through online book sellers. The atlas pro- vides both images of dust particles as well as insights into sampling methods and classifying dust particles by using various basic optical and simple spot test analyses (Jungreis, 1996). While we do not have to be exacting in identifying specific dust par- ticles, the particle atlas helps categorize dust into classes (i.e., biological and chemical),
from which we can infer its origin as well as postulate its potential for contamination. The third essential component is a basic optical microscope (any type) with a polar- izing lens or polarized light. A basic dust sampling field kit consists of an ATP (adenosine triphosphate) fluores- cence detector and surface testing swabs. The ATP kit measures biological “dirt” and is an essential tool for classifying dust, among other applications (Powitz, 2007, 2009). A UV (365 nm) flashlight and an LED white light (>200 lumens) flashlight show contrast and shadows of dust on surfaces, as well as those particles that are airborne. Clear microscope slides and transparent adhesive tape are used for lifting dust from the surface and axing it for count- ing and characterization. A thread counter or linen tester with a scale plate is used to measure the actual area on the slide. A good magnifying glass or loop magnifier can also be used. Lastly, an inspection extension mir- ror and some means to check air flow and air current help characterize the environment for interpreting air quality monitor data.
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June 2025 • Journal of Environmental Health
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