AIRBODS: Findings and guidance for airborne infection resilience, A publication of Airborne Infection Reduction through Building Operation and Design for SARS-CoV-2 (AIRBODS)

This guidance provides insights into airborne infection risks and proposes mitigation measures to improve airborne infection resilience of indoor and semi-outdoor spaces. In some poorly-ventilated and/or highly occupied spaces, the provision of increased ventilation performance can be the key to reducing airborne infection risk down to 'acceptable' (although currently undefined)levels. This is a complex area of study with many areas of uncertainty that form the basis of ongoing research. That said, the AIRBODS programme, in the context of the global research efforts associated with the COVID-19 pandemic, has generated a sound basis for improving airborne infection resilience. Key aspects of the guide with its many recommendations include:

• Experiments carried out in a test chamber showing how screens can improve or, even, worsen airborne infection risk.

• Field studies undertaken as part of the Events Research Programmewhichunderpinned the opening up of the UK hospitality sector in the summer of 2021. Good practice advice is provided on how to drive high-resolution CO2 and microbiological studies and then appropriately interpret results.

• Analyticalmodelswere developed to understand how infection risk, using a mass balance approach with many different parameters, might be mitigated in some circumstances when compared to reference spaces. These models were then developed into a 'full building' tool which can be downloaded as part of this guidance.

• Computational fluid dynamics (CFD) models were developed to provide insights into the physics of droplets or aerosols at microscale. Following completion of a test chamber validation exercise, models were developed to investigate breathing or coughing mannequins at single human moving towards audience or crowd scale. Local ventilation effectiveness and associated airborne infection risk aspects of some real spaces may significantly differ from assumed 'fully-mixed' equivalent spaces. This, along with a number of other issues, will form part of ongoing research activities.

• Focus groups were also used to provide some wider context and support some of our recommendations.

AIRBODS has produced a repository of data and modelling methods with the mindset of enabling building professionals to inform their design and operation decisions towards improving airborne infection resilience in their buildings.