<p>For the first time, the widespread model of spin exchange between paramagnetic particles in dilute solutions of paramagnetic particles is introduced as one paper. This model has served for decades as a useful tool for qualitative assessments when planning experiments and interpreting experimental results. It qualitatively interpreted peculiar manifestations of the spin exchange: the concentration broadening of the resonance lines in EPR spectra in the case of the slow rate of the spin exchange and the exchange narrowing of the EPR spectra when the fast rate of the spin exchange is realized. Here are presented results that do not agree with the widespread understanding of spin exchange in dilute solutions of paramagnetic particles. This widespread model of the spin exchange was never formally named a “paradigm”. But this set of ideas was widely accepted and shared by scientific community, functioned as one framework guiding how scientists understood and interpreted results concerning spin exchange. In light of shift to a new paradigm, which was presented in 2019, I refer to these widespread ideas and understanding of spin exchange as widespread paradigm.</p>