This work establishes 95% confidence level limits to models incorporating additional fermions sensitive to the strong interaction. Precision measurements of Transverse Energy-Energy Correlations at the ATLAS experiment are used, exploiting their dependence on the strong coupling constant to analyse the effects of introducing new fermions with colour charge on the Renormalisation Group Equation. The comparison between theoretical predictions, corrected up to next-to-next-to-leading order, and the data collected by ATLAS at $\sqrt{s} = 13$ TeV allows to constrain physics models proposing the existence of new fermions with masses up to 2 TeV, independently of assumptions on the fermion decay.
