[en] The sensitivity of imaging air Cherenkov telescopes (IACTs) worsens significantly at low energies because the γ/hadron separation becomes much more complex. In this paper we study the impact of single electromagnetic subcascade events on the efficiency of γ/hadron separation for a system of four IACTs using Monte Carlo simulations. The studies are done for two different altitudes of the observatory, three different telescope sizes and two hadron interaction models (GHEISHA and FLUKA). More than 90% of the single electromagnetic proton-induced subcascade events are showers with primary energy below 200 GeV, regardless of the trigger threshold. The estimated efficiency of γ/hadron separation using the FLUKA model is similar to results obtained using the GHEISHA model. Nevertheless, for at least one triggered telescope only, a higher fraction of single electromagnetic subcascade events was obtained from the FLUKA model. Finally, calculated quality factors are anti-correlated with the contributions of false γ-ray events in proton initiated showers. Therefore, the occurrence of single electromagnetic subcascade events is one of the main reasons for the worsening of primary γ-ray selection efficiency at low energies. (paper)