The concept of the mean free path is fundamentally important to aerosol studies. Recent studies suggest that the mean free path of air (λ_air) could have been significantly overestimated by a factor of ~2. Here we show that this potential overestimation does not directly affect collision-induced aerosol dynamics in atmospheric conditions without high excess latent heat, while a similar influence of the mean free path of vapor (λ) on aerosol dynamics has been accounted for in current studies.