Which of the following is a prohibited action for a security guard?

Sleeping on duty is a prohibited action for a security guard because it directly compromises the safety and security of the area they are responsible for monitoring. A security guard's role requires constant vigilance to detect and respond to potential threats, emergencies, or suspicious activities. Being asleep would significantly hinder their ability to perform these critical functions.

In contrast, conducting regular patrols is a standard practice for security guards, allowing them to assess the premises, ensure that everything is secure, and deter any criminal activity. Assisting in first aid efforts is also a vital component of a security guard's responsibilities when emergencies arise; being trained in first aid enables them to help individuals in need effectively. Documenting incidents is crucial for maintaining accurate records of any occurrences, which can be essential for investigations and legal proceedings. Therefore, while actions like conducting patrols, assisting with first aid, and documenting incidents are part of the duties and responsibilities of a security guard, sleeping on duty is explicitly prohibited as it undermines the guard's effectiveness and the overall safety of the environment.