Vertical transmission of infectious aerosols through building toilet drainage system: An experimental study.

The building's toilet drainage system has been identified as a potential route for the transmission of SARS-CoV-2 during outbreaks. This study employed agar-fluorescein sodium semi-solid as trace particles to investigate the possibility of vertical transmission of the SARS-CoV-2 in drainage system. In both scenarios, where floor drains were all properly sealed or dried out, simulated faeces containing fluorescein sodium were flushed into the toilet bowl. Air sampling was conducted in each restroom, and differential pressure measurements at the floor drain locations were taken. The experimental results showed that when all floor drains were properly sealed, the differential pressure at each floor drain was 0. The fluorescein sodium-traced aerosol did not transmit through the drainage system to various floors, which significantly reduced the risk of infection for users through this route. However, when all floor drains dried out, toilet users above the neutral pressure layer (NPL) were at a high risk of virus infection. Due to the increasing maximum negative pressure at the floor drain above the NPL with ascending floor levels, users on each floor above the NPL faced an elevated infection risk in restrooms. Specifically, users on the top floor were exposed to infectious aerosols roughly 1.6 times that of the first floor above the NPL. Conversely, owing to the increasing maximum positive pressure at the floor drain below the NPL with descending floor levels, users below the NPL experienced a comparatively lower infection risk. This finding has important implications for understanding the vertical transmission dynamics of SARS-CoV-2 in residential or public building and can inform the development of effective control measures.

Projeto piloto de uma caixa de descarga eficiente, econômica e à prova de vazamentos / Pilot design of an efficient, leak-proof and economical flush system

RESUMO Nas últimas décadas, houve redução de consumo per capita de água. Mesmo assim, diversos países buscam uma redução adicional no consumo por meio da melhoria dos processos de funcionamento de equipamentos. Este artigo descreve um novo design para caixa de descarga econômica, no qual não existe obturador nem juntas que possam ressecar e acarretar vazamento. Foram construídos e testados protótipos; o uso prolongado por 12 meses em uma residência habitada por quatro moradores demonstrou que o novo modelo de caixa de descarga funciona bem e consome menos água do que os demais. Esse projeto dispensa o uso de borrachas de vedação, trabalha com duas células (caixa interna e caixa externa), apresenta boa capacidade de arraste e demonstra boa eficiência tanto para descarga de 3 L como para descarga de 6 L.

ABSTRACT In the last decades, water consumption per capita has been reduced. Nevertheless, several countries look for additional reduction in water consumption through better process of equipment functions. This paper describes a new design for an economical flush system in which there is neither flapper nor gasket that could leak. Prototypes with new design have been made and tested; after a 12 months' test with one of them, by a family of 4 people, the project had good performance, with reduction in water consumption. This new design does not use gasket, works with two boxes (internal box and external box), presents good drag ability and demonstrates good water efficiency both for 3 L and 6 L flushes.