They are familiar to us from our TV screens: masks covering the nose and mouth, which are intended to provide protection against infection and are an everyday sight in Asian countries in particular. In the age of bird flu virus, SARS and influenza, the efficacy of such masks is also of increasing interest in our own part of the world.
The BG Institute for Occupational Safety and Health (BGIA) has now established that the majority of standard protective masks and cloths for the mouth and nose do not provide adequate protection against airborne pathogens. Of 16 products selected at random for a study, only three satisfied the essential requirements of DIN EN 149. This European standard defines binding performance criteria for respiratory protective devices used for occupational health and safety purposes. Firstly, the permeability of the filter material must not be excessively high: depending upon the filter class, it must not exceed between 2 and 22 percent of the concentration of hazardous substance present in the atmosphere. Secondly, the mask must fit flush against the wearer's face, in order for the protection offered by the product not to be impaired by leaks. The sum of these quantities is termed the total inward leakage. "The compliance of respiratory protective devices with these requirements is tested by an independent body," explains Dr. Peter Paszkiewicz, head of the department responsible at the BGIA. "Unfortunately, mouth/nose products (surgical masks) require no special approval. We have now studied whether and to what extent these products may nevertheless be suitable for use as breathing masks."
The results were as follows: of 16 products, four passed the filter permeation test, and four the total inward leakage test. Only three products satisfied both requirements. "But even when a highly effective filter material is used, up to 90 percent of the particles which are inhaled despite the mask can be attributed to leaks," emphasizes Paszkiewicz. "The form, flexibility, and fit of the mask on the face are therefore decisively important for its protective action."
The German Federal Ministry of Economics and Labour (BMWA) has already responded to the results obtained by the BGIA: in its body of regulations governing protection against influenza, it recommends the wearing of respiratory protective devices, or of mouth/nose masks satisfying the same performance criteria. To assist users in identifying in future which mouth/nose protection products fall into this category, the BGIA intends to publish a list of masks which have passed the tests. "We hope that the manufacturers will support us in this initiative and submit their products to testing," says the OH&S representative.
In their design, surgical masks resemble the filtering half masks employed for example at workplaces where protection is required against grinding dust. Airborne pathogens may be assumed to behave in the atmosphere in the same way as inanimate particles, not least because in practice, virii and bacteria are generally bound to liquids or dust. From an OH&S perspective, there is therefore no reason for surgical masks not to be made subject to the same requirements and tested under the same conditions as respiratory protective devices.
The comprehensive results can be found in this article (PDF, 2.1 MB).