Although Chem-I is a widely applied ionization technique, the degree of fragmentation and therefore the mass spectrum are highly dependent on the operation conditions, such as the analyte composition, temperature, pressure, presence of impurities (such as water vapor), etc. This leads to a poor reproducibility of Chem-I in general. Because of this, no such libraries of Chem-I spectra have been generated for compound identification so far. , , , The presented work aims to make researchers aware of the Chem-I scrambling issue and addresses the importance of carefully interpreting EIMS data.