The first attempts to quantify ion internal energy in ion sources used ions with sequential neutral losses (e.g., CO losses from ferrous complexes) . Later, De Pauw proposed instead to use series of Benzylpyridinium ions, each fragmenting via pyridine loss, with barriers depending on the substituent . During the last 20 years, several classes of thermometer ions, i.e., ions used to quantify the internal energy imparted to them, were also developed as complements to the benzylpyridinium salts. Benzylammonium ions are useful to characterize ambient ionization methods that require volatile analytes and not salts . We also survey these new thermometer molecules and gathered the highest quality values of their bond dissociation energies and threshold energies for the appearance of the fragments.