The concentration of virus in the circulating aerosol (Caero) is calculated by the formula:Caero=Cimp× VimpQimp× texp where Cimp is the concentration of virus (PFU/L), Vimp is the volume of collection fluid in the AGI (mL), Qimp is the sample flow rate of the AGI (L/min), and texp is the exposure time (min). Virus concentrations in Caero are converted to PFU/L to allow calculation against Cneb in PFU per litre of air sampled.