Under NZ (and Australian) law, employers can not delegate their health and safety responsibilities. They remain ultimately responsible for all health and safety breaches. Which is not to say they will be held liable. It all depends on the respective systems which are in place. Accidents do happen and will continue to happen. It all depends on whether an accident was foreseeable and whether the employer has done everything to prevent accidents from happening.
In Germany, however, we do things differently. There, an employer may delegate health and safety obligations to a suitably qualified employee and thereby discharging his responsibilities. There are rules around those kinds of delegation, of course. The employee has to have the respective qualifications in respect of the delegate health and safety duties. They must be properly instructed as to what there areas of responsibility are. In essence, they must be given a job description for their new tasks. Which all sounds very reasonable.
Sometimes things are easier then in Germany.