Comparison of the sampling characteristics of two vacuum surface samplers for the collection of dust mite allergen

Hand-held vacuum cleaners are commonly adapted for collection of allergens in settled dust; however, the collection efficiencies for most of these devices have not been investigated. We evaluated and compared the collection characteristics of two vacuum surface samplers: the ReadiVac (6735), a hand-held vacuum cleaner with a cloth filter bonnet; and the high volume surface sampler (HVS3), a modified upright vacuum cleaner equipped with a cyclone for collecting small particles and a means for adjusting the air flow in the sampler. The efficiency and precision of the two vacuum samplers were evaluated by vacuum sampling 30 matched-pair carpet samples doped with house dust containing dust mite allergen. The HVS3 recovered twice as much bulk dust and four times as much allergen as the ReadiVac, although the intake velocities of the two samplers were practically equivalent. The correlation of bulk dust recovery with allergen recovery by the ReadiVac was r = 0.54 compared with the HVS3’s of r = 0.90. These findings suggest that the ReadiVac sampler collection efficiency appears to have a significant particle size bias, which has important implications for the normalization of exposure results using the mass of bulk dust collected as the denominator. New reporting conventions for allergen exposure should be evaluated, and more efficient hand-held allergen collectors are needed.