What feature is essential in a safety helmet used in high temperatures?

The essential feature in a safety helmet used in high temperatures is a heat-resistant outer shell. This characteristic is crucial because it provides the primary defense against high temperatures and potential fire hazards. Heat-resistant materials help prevent the helmet from melting or deforming in extreme conditions, which could expose the wearer to serious injuries.

While thick inner padding, wider brims, and additional ventilation holes contribute to comfort and usability, they do not address the fundamental requirement of protecting the wearer from heat-related dangers. The outer shell's ability to withstand extreme heat is what ensures the helmet effectively protects the head in environments where high temperatures are a risk, making it the vital feature needed for safety in such conditions.