GUIDANCE | AIR CLEANING DEVICES A new CIBSE guide aims to equip specifiers and facilities managers with the knowledge to safely and effectively select air cleaners. Cundalls Ed Wealend summarises the contents A NOVEL APPROACH: AIR CLEANING DEVICES I n July, CIBSE published the new Covid-19: Air cleaning technologies guide as part of its series Emerging from lockdown. The world of air cleaning devices is extremely complex. This guide aims to help engineers and building managers to assess whether an air cleaning device might be beneficial, and whether the device they are considering is fit for purpose and, above all, safe. The guide gives a brief introduction to removal mechanisms for SARS-CoV-2, a summary of the existing guidance related to the different technologies employed for air cleaning, and several tools and worked examples to help specifiers determine the potential impact of an air cleaner introduced into a space. Chief among these is the Relative Exposure Index Calculator. This article gives a brief introduction to the topics covered in the guide. Government statutory guidance on Covid-19 safety should be followed at all times. Air cleaning devices should not be used as a substitute for adequate ventilation. can be applied to reduce infection risk, particularly from airborne particles carrying SARS-CoV-2. As SARS-CoV-2 is a relatively new virus, there is not a large body of research on the specific effectiveness of any technology for application against it. However, organisations including the World Health Organization (WHO) and the Scientific Advisory Group for Emergencies (SAGE) have reviewed the literature that does exist and made recommendations based on the best available evidence. The new guide summarises these recommendations. There is also a lack of guidance on the specification and selection of air cleaning devices, especially in commercial settings such as Ventilation Momentuminduced deposition Biological decay Suspension Old approaches to a new problem Devices that clean the air have existed for many years. They range from the well known, such as mechanical filtration, to more novel and less studied methods, which employ a variety of catalysts, ionisers, electrostatic or other techniques to physically or chemically alter particles passing through them. Historically, many of these devices were marketed for the removal of chemical pollutants, such as volatile organic compounds (VOCs) or particulates, with less of a focus on pathogens. With the emergence of Covid-19, attention has turned to how these devices HVAC Inhalation Emission Ventilation Deposition and ballistic deposition Figure 1: Single-zone mass-balance model of virus transport via exhaled aerosols1 58 September 2021 www.cibsejournal.com CIBSE Sep 21 pp58-61 Air cleaning devices.indd 58 27/08/2021 13:01