The accumulation of dust, proteins and allergens from alder, birch, timothy, cat, dog, mite, hen egg white, codfish and mould in schools was investigated by analysing the content of vacuum cleaners after 10 days of use. The main goals were to compare the dust accumulation on carpeted and smooth floors and to estimate to what degree the three vacuum cleaner filter stages (i.e. the disposable bag, the main filter and the microfilter) collected dust, proteins and allergens. Carpeted floors accumulated more dust, proteins and allergens per unit area than smooth floors. Histamine release studies of some of the dust extracts showed that the dust from carpeted floors released histamine from passively sensitized basophils at concentrations for which dust from smooth floors gave low or no histamine release. The analyses showed that most of the dust, proteins and allergens were retained in the dust bags. Less than 1 % of the vacuumed material had accumulated in the main filters, which, according to the manufacturer, detain 99.5% of particles > 2 pm. By the use of a scanning electron microscope (SEM), particle deposits were observed in the microfilters. These deposits, which represented < 0.1 % of the total mass, showed no significant allergenic activity. Thus, for the field conditions of this study, the microfilters were not needed for cleaning the exit air of allergens, although they were useful for removing fine (< 2 pm) particles. CLINICAL ASPECTSCarpeted floors accumulated more dust, proteins and allergens per unit area than smooth floors. Allergens included in dust from carpeted floors released histamine from passively sensitized basophils at concentrations for which dust from smooth floors gave low or no histamine release. Most of the dust and allergens were collected in the dust bags during vacuuming. Less than 1 % of the total vacuumed material passed through the dust bags further to the main and microfilters during vacuuming. The allergenic activities of dust from the main filter were low, even after removal of molecules with M,<3500 daltons by dialysis. By scanning electron microscopy we could clearly observe particle deposits in the third and final filter stage, the microfilter. These deposits showed little or no allergenic activity.The cleaning efficiency of commercial vacuum crease the number of airborne particles of dicleaners will usually differ from model to ameters > 0.5 pm (10). Thus, the paper bag model. Vacuum cleaning of carpets can in-used in vacuum cleaners without subsequent

Summary Optical diffraction tomography (ODT) is used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres. The selected fibres were polymer and animal fibres of either circular or non‐circular cross‐section with average thicknesses in the range 8–110 μm. This choice of samples was made to illustrate the imaging capabilities of ODT, and also to demonstrate some potential applications of the technique. The images representing the reconstructed refractive index distributions have a spatial resolution of about 2 μm, and show noticeable image contrast for refractive index variations of about 0·001. The ODT reconstructions compare well with refractive index information provided with the samples, and with scanning electron micrographs of cross‐sections of the same fibre samples. From these results it appears that ODT can be used to reconstruct the complex refractive index distribution in cross‐sections of semi‐transparent, birefringent fibres.

The accumulation of dust, proteins and allergens from alder, birch, timothy, cat, dog, mite, hen egg white, codfish and mould in schools was investigated by analysing the content of vacuum cleaners after 10 days of use. The main goals were to compare the dust accumulation on carpeted and smooth floors and to estimate to what degree the three vacuum cleaner filter stages (i.e. the disposable bag, the main filter and the microfilter) collected dust, proteins and allergens. Carpeted floors accumulated more dust, proteins and allergens per unit area than smooth floors. Histamine release studies of some of the dust extracts showed that the dust from carpeted floors released histamine from passively sensitized basophils at concentrations for which dust from smooth floors gave low or no histamine release. The analyses showed that most of the dust, proteins and allergens were retained in the dust bags. Less than 1% of the vacuumed material had accumulated in the main filters, which, according to the manufacturer, detain 99.5% of particles greater than 2 microns. By the use of a scanning electron microscope (SEM), particle deposits were observed in the microfilters. These deposits, which represented less than 0.1% of the total mass, showed no significant allergenic activity. Thus, for the field conditions of this study, the microfilters were not needed for cleaning the exit air of allergens, although they were useful for removing fine (less than 2 microns) particles.

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