The filling of a powdered antibiotic, which has been ongoing for decades, takes place in a RABS within an AB room. The previous formaldehyde fumigation was no longer up-to-date, leading to a search for alternatives. This was found in H2O2 decontamination, with the goals of both keeping costs low and avoiding extensive structural modifications. This presentation will cover the definition of the system, technical and structural limitations, the challenges during and after implementation, automation, and the execution of cycle development and validation. This presentation is of interest to anyone seeking a straightforward and cost-effective optimization of their cleanroom decontamination.