Which principle of first aid ensures that the casualty is safe from further harm?

A fundamental principle of first aid is to ensure the safety of the casualty, the bystanders, and the first aider. This is often summarised as the "3 Ps" of first aid: Preserve life, Prevent deterioration, and Promote recovery. Preventing further harm falls directly under the second P.

The correct approach is to remove the casualty from danger if it is safe to do so. Before providing any treatment, a first aider must assess the scene for hazards such as traffic, fire, electrical wires, collapsing structures, or chemical spills. If the environment is dangerous and the first aider can safely move the casualty without worsening their injuries, they should do so. If moving the casualty is too risky, the first aider should try to eliminate the hazard instead.

Calling an ambulance before checking the surroundings could put both the first aider and the casualty at continued risk from an unrecognised hazard. Giving food and water is generally not recommended for a casualty, as they may need surgery (which requires an empty stomach) or may have difficulty swallowing. Ignoring hazards is dangerous and contradicts the core safety principle of first aid, which always begins with scene assessment.