Industrially important plasmas offer a variety of complicated molecular processes that benefit from predictive quantum chemical techniques. Ab initio coupled-cluster and MBPT methods are used to characterize structures, vibrational frequencies, ionization potentials, electron affinities, and excited states for the main fragments in the BCl3 plasma, i.e. BCl3, BCl2, BCl, and their anions and cations for which few experimental results exist. The excited, electron attached, and ionized states are calculated by employing the equation-of-motion coupled cluster (EOM-CC) method. Recent results from a photofragmentation study and an electron collision experiment are analysed based on the calculated results. Some features of the potential energy surfaces of excited states of BCl2 are discussed in order to explain the origin of the experimental fluorescence spectrum. We also consider possible microscopic processes with low energy, such as the formation and destruction of neutral and ionic species, decomposition paths, and the role of each fragment. While decomposition through transient states of BCl3- by electron attachment is the most probable path for low-energy electron attachment, decomposition through excited states of BCl3 can play a role only when there is no other way to make the BCl3+ ion.