Existed evidences show that airbe transmission of human respiratory droplets may be related with the spread of some infectious disease,such as severe acute respiratory syndrome(SARS)and H1N1 pandemic.Non-pharmaceutical approaches,including ventilation system and personal protection,are believed to have certain positive effects on the reduction of co-occupant’s inhalation.This work then aims to numerically study the performances of mouth covering on co-occupant’s exposure under mixing ventilation(MV),under-floor air distribution(UFAD)and displacement ventilation(DV)system,using drift-flux model.Desk partition,as one generally employed arrangement in plan office,is also investigated under MV.The dispersion of 1,5 and 10 μm droplet residuals are numerically calculated and CO2 is used to represent tracer gas.The results show that using mouth covering by the infected person can reduce the co-occupant’s inhalation greatly by interrupting direct spread of the expelled droplets,and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person.The researches under MV show that the two interventions,mouth covering and desk partition,achieve almost the saroe inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.