  In this work we investigate the properties of the broad emission line
components in the Balmer series of a sample of Type 1 Active Galactic Nuclei
(AGN). Using the Boltzmann Plot method as a diagnostic tool for physical
conditions in the plasma, we detect a relationship among the kinematical and
thermo-dynamical properties of these objects. In order to further clarify the
influence of the central engines on the surrounding material, we look for
signatures of structure in the broad line emitting regions, that could affect
the optical domain of the observed spectra. Using a combination of line profile
analysis and kinematical modeling of the emitting plasma, we study how the
emission line broadening functions are influenced by different structural
configurations. The observed profiles are consistent with flattened structures
seen at quite low inclinations, typically smaller than 20 degrees. Since this
result is in good agreement with some independent observations at radio
frequencies, we apply a new formalism to study the properties of AGN central
engines.
