COVID-19 | REHVA GUIDANCE PREVENTING COVID-19 SPREADING IN BUILDINGS In response to the coronavirus pandemic, REHVA experts have published a guidance document on how to operate and use building services to minimise the spread of Covid-19. Alex Smith provides a summary of their findings R EHVA, the Federation of European Heating, Ventilation and Air Conditioning Associations, has produced interim guidance on the operation and use of building services in areas with a coronavirus disease (Covid-19) outbreak. Based on a survey of recent academic literature, the guidance aims to prevent the spread of coronavirus through HVAC or plumbing systems, and is targeted primarily at HVAC professionals and facility managers. Its scope is limited to commercial and public buildings, such as offices, schools, shopping areas and sports premises, where only occasional occupancy by infected people is expected. Information and research on the disease and virus responsible for it (SARS-CoV-2) is very limited, so REHVA says bestpractice recommendations have been made based on evidence from SARS-CoV-1, which occurred in 2003-04. The document will be updated with more information and evidence when it becomes available. Transmission routes The guidance document states that there are two dominant transmission routes: via large droplets (droplets/particles emitted when sneezing, coughing or talking); and via surface contact (hand-to-hand, hand-tosurface, and so on). However, it says the World Health Organization (WHO) also recognises a faecal-oral transmission route for SARS-CoV-2. In a technical briefing on 2 March, WHO recommended closing toilet lids when flushing, and avoiding dried-out drains in floors and other sanitary devices by regularly adding water (every three weeks, depending on climate). In the SARS 2003-04 outbreak, open connections with sewage systems appeared to represent the primary transmission route in the Amoy Gardens apartment building in Hong Kong. Transmission was probably because of a dried-out floor drain and airborne dissemination by the toilet exhaust fan and winds. Professor Catherine Noakes, professor of environmental engineering for buildings at Leeds University, says aerosolisation from water systems may be important. The REHVA guidance recommends checking floor-drain traps, but drain traps in high-rise buildings can be susceptible to being blown out by wind pressure. So even traps in drains that are used more regularly are important to watch, too. Air transmission There are two exposure mechanisms, which the guidance document describes as follows: Large droplets (> 10 microns) Airborne transmission through large droplets that are released and fall to surfaces no further than 1-2 metres from the infected person. Droplets are formed from coughing and sneezing (the latter typically forms more particles). Most of these fall on surfaces such as desks and tables. People could catch the infection by touching contaminated 26 April 2020 www.cibsejournal.com CIBSE Apr20 pp26-28 Coronavirus.indd 26 20/03/2020 17:06