Colliding respiratory jets as a mechanism of air exchange and pathogen transport during conversations

Air exchange between people has emerged in the COVID-19 pandemic as important vector for transmission of SARS-CoV-2 virus. We study airflow and two unmasked individuals conversing face-to-face at short range, which can potentially transfer a high dose pathogen, because dilution is small when compared to long-range airborne transmission. conduct flow visualization experiments direct numerical simulations colliding respiratory jets mimicking initial phase conversation. The evolution dynamics are affected by vertical offset mouths speakers. At low offsets head-on collision results `blocking effect', temporarily shielding susceptible speaker from pathogen carrying jet, although, lateral spread enhanced. Sufficiently large prevent interaction jets. intermediate (8-10 cm 1 m separation), jet entrainment inhaled breath assist transport pathogen-loaded saliva droplets towards speaker's mouth. expected, spite blocking effect arising