DESIGN AND CALIBRATION OF A SIMPLE INSTRUMENT FOR MEASURING DUST ON SURFACES IN THE INDOOR ENVIRONMENT

A simple method for quantifying dust on indoor non-textile surfaces ha s been developed and evaluated. The method uses gelatine foils to samp le particles from surfaces, applying a constant pressure. The foils po ssess unique properties, making them particularly suitable for evaluat ion by light extinction. The amount of particles collected as measured by laser light extinction is expressed as the area percentage covered by particles. Foil sampling effectiveness has been estimated to range from 87% to 97%. A simple method for calibrating the instrument has b een developed. The relation between the total projected particle area excluding overlap can be determined from the measured projected area i ncluding overlap from a simple equation. An overall uncertainty is giv en, including effects of positioning foils in the detector, sampling f rom rough surfaces, and the natural variability due to the discrete na ture of particles. The lower level of detection for dust on an object is less than 0.5% surface area covered by dust. The method has formed the basis for suggesting a sampling strategy and surface dust limits i n relation to cleaning and the quality of the indoor environment.