The influence of the position of the infected occupant (infector) with respect to the healthy occupants (susceptible) in the indoor environment is generally unknown and changes through time due to occupants’ movement. This paper examines the dependence of protective performance of four different ventilation systems (mixing, displacement, underfloor and personalized) on the distance between infected and susceptible occupants (i-s distance) at 6 and 12 ACH. Exposure of the occupant was measured in a Field Environmental Chamber and those results were averaged and analysed with a dose–response model to estimate risk of getting infected for Influenza and Tuberculosis (TB). Major findings form the study are: (i) all systems exhibit increase in probability of getting infected (P) at i-s distance of 2 m compared to 1 m; (ii) increase of i-s distance beyond 2 m reduces risk of airborne infection disease transmission; (iii) all total volume system have similar P values for i-s distance of 4m; (iv) desktop personalized ventilation has the best performance, while among total volume systems displacement ventilation has the best performance in achieving the lowest risk values for Influenza at 6 ACH. For Tuberculosis averaged results at 6 ACH show that: (i) mixing and desktop personalized ventilation reduce risk values with the increase of i-s distance; (ii) MV has the lowest risk values among total volume systems. Averaged results at 12 ACH for Influenza and TB demonstrate that desktop personalized ventilation has the best protective ability among all systems at all i-s distances and is the only system able to reduce P values with increase of i-s distance. At 12 ACH for Influenza, among total volume systems mixing ventilation performs the best; while for TB, displacement ventilation performs the best among total volume systems for i-s distances larger than 1 m.