More completely, using the model predictions, we identify the volume fraction of respiratory droplets in the initial diameter size range <100 µm from a cough that remain at an elevation above 1 m at each of the separation distances whilst varying RH whilst keeping temperature constant at 293 K (Fig ) and temperature whilst keeping RH constant at 50% (Fig ). Specifically, we divide the particle size distribution into 2 halves, those that are too large to remain airborne and have trajectories that take them below 1 m above the ground at the chosen separation distance, and those that are sufficiently small to remain elevated above 1 m. We then integrate the volume concentration distribution, determining the fraction in the volume distribution that remains elevated above 1 m where the volume fraction can be expected to provide a good estimate of the mass fraction. The size distribution reported by Johnson et al. is assumed to be the initial distribution of droplet sizes (Fig ).