The ventilation factor gives us a way of relating the pollution concentration to the parameters that control dispersion of the pollution in the local environment. Basically, increasing either the mixing height or the wind speed increases the effective volume in which pollutants are allowed to mix. And, the larger the volume, the lower the pollution concentration (as we saw in the box model). Thus, the overall concentration of pollutants tends to decrease as the ventilation factor increases (assuming the pollution source rate is constant).