To prevent burns, a heating blanket should not be placed where?

A heating blanket should not be placed directly on the casualty's skin to prevent burns because direct contact can cause overheating and thermal injury, especially if the skin is sensitive or if the casualty has impaired sensation. Heating blankets are designed to warm a person gradually, and placing them directly on the skin can lead to hot spots, which could cause burns before the casualty can react to the heat. Instead, it's preferable to place the heating blanket over clothing or a thin layer, allowing for better control of temperature and reducing the risk of burns.

Additionally, the other options do not carry the same risk: placing a heating blanket over the casualty's head can help retain heat but does not cause burns; wrapping it around legs provides warmth without direct skin contact; and placing it under a regular blanket offers insulation, enhancing the heating effect without risk of direct thermal injury.