[Encasing evaluation: studies of dust retention and water permeability]

The use of allergenproof mattress casings for those allergic to house-dust mite is a vital component of therapeutic concepts concerning the avoidance of allergens. Encasings of different materials are available from a variety of manufacturers on the German market. The goal of this study was to investigate different encasing materials to test for their impermeability to dust and permeability to water vapour ("breathability"). Material samples from nine different manufacturers as well as one additional samples were tested by two independent institutes. The samples were coded with serial numbers and the product names and manufacturers were unknown to the testers. The degree to which particles could penetrate the materials (as a measure of dust penetration) was tested in two series of experiments using the naturally available ambient air and fine coaldust. A thermo-regulation model ("skin model") was used to test the materials for water vapour permeability. The results of three of the nine samples tested for particle penetration have to be considered unsatisfactory due to the number and size of the particles allowed to enter. Overall an additional synthetic layer appears to improve the materials capacity to prevent dust penetration. The water vapour permeability of three of the nine samples of encasing material must be classified as unsatisfactory with the consequence of possible sleep disturbance. From an allergological point of view, minimal particle penetration is an essential criteria. On the other hand, low water vapour transport properties can diminish the patients willingness to comply. The present study cannot be substituted for a clinical study of effectiveness but nonetheless reveals, in some cases, considerable differences in the physical properties of the various materials. It would be desirable for the individual product packaging to feature a declaration of the relevant test data, thus providing decision-making for those buying or prescribing.