High risk construction work requires preparation for emergencies. You may need to provide a rescue plan and equipment to cover specific activities, for example electric shock, fall in a harness, EWP decent and confined space work. Your procedure may be a templated one that is tailored to the specific circumstance, including the nomination of who will perform which task if required. Everyone involved in a rescue plan must be trained on it and any specialist rescue equipment should be on hand. Relying on calling public emergency services is not a substitute for providing rescue equipment and training.