Optimized portable cordless vacuum method for sampling dry, hard surfaces for dusts

Surface sampling in industrial/environmental hygiene is a growing field that needs validated standardized methods. There are few standard methods, one being the American Society for Testing and Materials (ASTM) method involving a portable, cordless air sampling pump. In the present work, the ASTM technique was modified to increase efficiency and versatility. A soil sample was first dried and sieved. Known weights of different sieved sizes (125 microns-180 microns, 90 microns-125 microns, and 63 microns-90 microns) were then sampled at an average flow rate of 4.0 +/- 0.2 L/min from a template of inner dimensions 10 cm by 10 cm on two different surfaces (rough and smooth). Five consecutive sampling passes were performed. For the smooth surface, the first pass efficiency for the largest particles were 45% +/- 45% (CV = 100%), and 75% +/- 20% (CV = 27%) for the smallest particles. After three passes, the efficiency independent of particle size exceeded 83 percent with a CV better than 11 percent. After five passes, the efficiency exceeded at least 85 percent with about the same precision as for three passes. The rough surface allowed higher efficiencies for the first two sampling passes. Three to five passes are recommended to achieve acceptable efficiencies for the surface loose dust/soil range 100 micrograms/cm2 to 1,500 micrograms/cm2.