Decontamination of room air and adjoining wall surfaces by nebulizing hydrogen peroxide

Aim: In 2010, the ASP GLOSAIR(TM) 400 was introduced in Germany for nebulizing hydrogen peroxide (H(2)O(2)). Since there were no results of practical experience, the new method was to be checked under practical conditions for its effectiveness in decontaminating air in rooms, infested with mold after water damage and, at the same time, under experimentally controlled conditions, test surfaces, contaminated with Aspergillus brasiliensis. Method: After the nebulizer was used in two rooms with a massive mold infestation, the air colony count was determined (MAS-100(®) Zinsser Analytik) and, at the same time, the mold infestation in samples of wall plaster. As part of this controlled study, test surfaces contaminated with Aspergillus brasiliensis were positioned vertically and horizontally in a test room. The effectiveness of the nebulization (5–6% H(2)O(2) for 2 hours) was tested on these surfaces according to EN 13697. Results: In a massive mold infestation resulting from water damage (worst case), an approximately 9-fold decrease in the mold content and an approximately 13-fold decrease in the number of colony-forming units (sum of the bacteria + fungi) could be detected in the room air immediately after the nebulizing was finished. Even in samples of wall and joint plaster, the molds were reduced, although to a distinctly lesser extent. By indoor nebulization of 5–6% H(2)O(2), A. brasiliensis was reduced >4 log on vertical and horizontal surfaces. Discussion: In rooms with a massive mold infestation, the ASP GLOSAIR(TM) 400 system is suitable for attaining a clear reduction in the fungal and bacterial room air load, lasting for a week. On vertical and horizontal surfaces, contaminated experimentally with A. brasiliensis, a reduction of >4 lg is achieved. As a load of 10(4) to 10(5) fungal spores is unlikely to occur on pre-cleaned surfaces, the GLOSAIR(TM) 400 can be considered a suitable complementary process for the substantial reduction of fungal contamination.