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7697002 
Journal Article 
Air hygiene in classrooms under SARS-CoV-2 conditions - Part I: Effects of noise exposure when using mobile air purifiers (MAP) 
Steffens, T; Seipp, HM; , 
2021 
Yes 
Gefahrstoffe, Reinhaltung der Luft / Air Quality Control
ISSN: 0949-8036
EISSN: 1436-4891 
SPRINGER-V D I VERLAG GMBH & CO KG 
DUSSELDORF 
127-134 
WOS:000645246400009 
Setting high-level acoustic requirements to ensure teachers have healthy working conditions in school classrooms and pupils learn successfully requires the sound from air conditioning systems to be limited to <= 35 dB(A). However, considerable structural defects in classrooms have been extensively documented and excessive reverberation times have been identified. The continuous sound from mobile air purifiers (MAP) would further aggravate the exposure limits, which have already been exceeded in many places. Depending on the number of MAP and the level of continuous sound, teachers are forced to speak louder (Lombard effect), which leads to a significant increase in the release of (viral) particles. In order to ensure the level of speech intelligibility required by DIN 18041 reaches every seating position in the room, even during continuous operation of the MAP (54 dB(A)), the teacher must increase their volume considerably. Depending on the position in the room, MAP induce 4.2 or 11.2 times higher (viral) loads, to which all those present in the classroom are exposed.