Taratura delle apparecchiature e stima dell'incertezza di misura nella valutazione microbiologica dell'aria indoor

Indoor air contains a complex mixture of microorganisms, microorganism fragments, and byproducts such as endotoxins, mycotoxins, and volatile microbial organic compounds. Bacteria, fungi, viruses, protozoans, and microscopic animals have been linked to poor indoor air quality. The air sampling in confined spaces can be monitored by active and passive methods; in active monitoring a microbiological air sampler physically draws a known volume of air through or over a particle collection device which can be a liquid or a solid culture media and the quantity of microorganisms present is measured in CFU (colony forming units)/m3 of air. Among the most commonly used active sampling systems there are single-stage samplers with orthogonal impact, such as the Surface Air System (SAS); such equipment ensure the removal of high volumes of air, but do not allow the direct intake flow control. Air microbial sampling is a subject of great interest in different fields of human activity, however, generally accepted indications, concerning both the sampling methods to be used and the interpretation of the results, are still lacking; furthermore, it has been known that different active samplers show high variability giving different results in the same place at the same time. The use of a system, connected to the instrument and that consists of a Pitot tube and a manometer, has allowed (with the monitoring of environmental conditions and with fluid dynamic calculations) to determine indirectly the sampled air volume. Evaluation of repeatability for both sampling and analytical phases and the subsequent statistical analysis of data, provided evidences for estimation of the associated uncertainty (carried out both the metrological and the Monte Carlo methods). The implementation of the traditionally adopted official method for the determination of bioaerosols, will allow its use for the competence of testing and calibration laboratories (UNI CEI EN ISO / IEC 17025: 2005) in accordance with the general requirements.