Chemical, manufacturing and refining processes often generate toxic liquid by products that are emitted as liquid aerosols in the waste stream. Wettable and nonwettable fibers can be used to filter these exhaust streams. The behavior of liquid aerosols and droplets on nonwettable fibers is studied by observation measurement and theory. Droplets form on the fibers, grow by accretion from the aerosol, oscillate, and then fall under the action of gravity. Observation and theory indicate that these developing droplets influence air and aerosol flow strongly in the filter: These droplets are akin to the dendritic structures formed by solid aerosol particles within filters, but the shapes are modified by surface tension. The total efficiency of the filter is influenced by these droplets, and the total filter efficiencies are estimated using theoretical methods. The results from both approaches agree excellently in the particle-size range as measured using particle-counting techniques.