An improvement to an operational system of a module for locking injection devices of a subsystem for applying substances into fertile eggs represents an inventive solution in the field of poultry farming, in particular in the field of poultry breeding and more specifically in the step of application of vaccines and/or nutrients into fertile eggs (Ov), wherein the locking submodule (m1) of the subsystem for applying substances into fertile eggs has a distinguishing concept, the locking and stabilising of each injection device (I) by at least three inflatable elements (12) mounted side by side in respective adjacent openings (11b), and a pressure recognition submodule (m5) is provided under operational optics to allow the management submodule (m2) to decide whether to start the substance inoculation module.
