Starting from Hagen-Poiseuille's law, we analyzed the parameters influencing fugitive emission rates. It is shown that liquid and gas emissions follow basically different mass transport mechanisms so that mathematical models available for gases are not suitable to calculate liquid emissions. The emission behavior of liquid-charged flange joints is characterized, and a model conception for the observed phenomena is presented explaining the unexpectedly high emissions of liquid-charged flange joints. Against the background of field data, the influence of maintenance on fugitive emmissions is demonstrated, and exchanging old gaskets with high-grade gaskets as a means of emission reduction in old plants is critically scrutinized. A general maintenance plan is proposed as the most effective method for emission reductions.