Lessons from the coronavirus pandemic: a review of how the disease spreads in indoor spaces

In the post-coronavirus era, it is important to understand how infections spread in the indoor environment. The modes of transmission that are of interest to this research are droplet-borne and airborne transmission. In these transmission cases, there is a dependency on air to transport pathogens. The buoyancy of pathogens depends on the mass of the particles or droplets, volume of the indoor space and air velocity. Understanding this is key to reaching a sound methodology for control. The case studies consist of two main groups: the first group is research based published prior to the onset of the pandemic, and the second group is based on studies of actual infection cases subsequent to the onset of the pandemic. When examining the cases, it is apparent that the three main factors that are constantly recurrent are population density, airflow rate and air recirculation. In a lot of cases, air stagnation and lack of air change are conclusive causative factors of infection transmission, while in a couple of cases, it was shown that infective agents can travel more than 3 m, another factor to be taken into consideration. When there is a total lack of airflow and air change, population density becomes the main causative factor. This research presents a set of guidelines for the ventilation of spaces in different types of indoor environment through exploring the role of the built environment in the transmission of infection and how building design can effect change on public health.