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Feature 6 www.thefis.org A new British Council for Offices (BCO) research paper, Thoughts on ventilation design and operation post COVID-19 , has called for UK offices to ensure they have adequate ventilation ahead of the return to the workplace. WHAT ARE YOU BREATHING? I NDOOR air quality (IAQ) refers to the air quality within and around buildings with particular emphasis on how it relates to the health and comfort of occupants, and the BCO research paper highlights that while most offices that follow good practice guidelines do benefit from good ventilation, there are also many examples of poorly ventilated offices that fall short of the best practice guidelines set out in the BCO’s 2019 Guide to Specification. Poorly ventilated indoor spaces have been linked to COVID-19 super spreader events and the paper states that ventilation in these offices must be “addressed urgently.” Recent advice from the UK Government highlights the importance of good ventilation in fighting COVID-19, citing research which shows that being in a well ventilated space can reduce the risk of infection from airborne particles by more than 70%. What’s more, the benefits of a well ventilated space go beyond mitigating the pandemic, with research showing a clear link between good ventilation and improved health and wellbeing. The paper recommends that: • as a minimum, levels of outdoor air ventilation should be in line with the new BCO guidance; • particular attention should be given to high occupation density spaces, such as conference suites, social hubs and meeting rooms to ensure they have an adequate outdoor air supply and exhaust air ventilation; • avoid the use of air recirculation in central ventilation plants; • provide facilities management professionals with training to help them to address indoor ventilation challenges effectively and to ensure systems are properly maintained and their performance monitored; and • continuously monitor indoor air quality and maintain CO 2 levels below 1,000 ppm. The paper discusses the potential use of air-cleaning technology to remove viral particles from the air, but emphasises that they are not a substitute for ventilation and should not be used as a reason to reduce outdoor ventilation rates. Long-term benefits of good office ventilation Lead author of the report, Derek Clements-Croome, Professor Emeritus at University of Reading, said: “Ensuring a high standard of indoor air quality may be the most important thing we can do to fight COVID-19, combined with social distancing, washing our hands and wearing masks. Yet too many UK offices have inadequate ventilation. Germany is providing finance to upgrade ventilation systems in buildings and the UK Government should consider doing this too. “The importance of good office ventilation to maintain the general health and wellbeing of occupants is well understood, but the deeper understanding we now have of how it can help reduce the risk of airborne disease transmission following the experience of COVID-19, has provided a new impetus to improve things further. Doing so will bring long-term benefits. Offices that enjoy better indoor air quality conditions also tend to be occupied by happier, healthier and more productive workers.” Neil Pennell, Head of Design Innovation and Property Solutions at Landsec and Chairman of the BCO Technical Affairs Committee, said: “The pandemic has created a significant shift in the expectations of office users. A stronger focus on providing clean, hygienic and well ventilated spaces are now central factors in providing safe workplaces and will be expected by employees as they return to their offices. Well ventilated spaces are not only essential in terms of physical health benefits, there is also a clear link between good ventilation and improved mental wellbeing.” Richard Kauntze, Chief Executive of the BCO, said: “Naturally, we’re pleased that offices can reopen – however, we want to make sure that the transition is as safe as possible. Offices should have a high standard of ventilation, not only to combat COVID-19, but also to aid the long-term wellbeing of workers.” 1 longer.The inverseof this ratio ( Q / V )gives theair change rate (thenumberofair changesperhour). Valuesof theair-change rateare specified invarious guides toventilation foravarietyof spaces,but it should be remembered that thesevaluesdonot take intoaccount the impactson the rateof transmissionof infection.Elovitz andElovitz 2 and theFederationofEuropeanHeating, VentilationandAirConditioningAssociations (REHVA) 3 haveattempted todo this in the results theyhave reported. THOUGHTS ON VENTILATION DESIGN AND OPERATION POST COVID-19 Supplementary material and bibliography Wells–Riley risk assessment model TheWells–Rileymodelhasbeenusedextensively for thequantitative riskassessmentof infectionwith respiratorydiseases in indoorpremises. Ithasalsobeen usedextensively toanalyseventilation strategiesand theirassociationwithairborne infections in clinical environments. Airborne concentrations canbe related to infection risk using theWells–Rileymodel for specificventilation rates: 1 N = S [1–exp (– λt )] where N is thenumberof casesaffectedover time t , S is the numberof susceptiblepeople in the space suppliedwithair at Q m 3 /s,and λ = Iqp / Q where I is thenumberof infectiouspeople, p is the pulmonaryventilationorbreathing rateof susceptible individuals (m 3 /h)and q isaunitof infection (aquantum) that represents the responseof susceptible individuals to inhaling infectiousdroplets (expressedas thenumberof viralparticlesperhour). ElovitzandElovitz 2 used influenzadata to calculate valuesof p and q .Theyproposedavalue for p of0.5m 3 /h foradults,andvalues for q of10 (sittingandbreathing normally),34 (standingorwalkingandbreathing normally),320 (sittingand talking)and1030 (standingor walkingand talking)viralparticlesperhour.While these arenotabsolutevalues,andarenotbasedonCOVID-19, they canbeused toobtainan indicationof the rateof infectionand the roleofventilation in thisprocess. The same studyalso lookedat theprobabilityof infection withvariousair supply ratesexpressedas thenumberof air changesperhour (seeTable1 inElovitzandElovitz 2 ). Besides theairflow rate ( Q ), thevolumeof the space ( V ) is important,because V / Q gives theageof theair.Ahigh valueof V / Q indicates stagnantand stuffy conditions, whichwouldmean that thevirus remains in the space for British Council for Offices Briefing Note February 2021 Source:AllanSwart |AlamyStockPhoto Continued on page 8

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