Philadelphia Fire Department Practice Exam

Above what air movement speed can heat transfer to the body significantly increase, according to the research?

1. Two mph

2. Five mph

3. Seven mph

4. Ten mph

The correct answer is: Ten mph

Heat transfer to the body through convection significantly increases at higher air movement speeds due to the enhanced removal of heat from the skin's surface. Research indicates that once air movement reaches speeds around ten mph, the body experiences a considerable increase in heat loss, which can be significant, especially in hot environments. Air movement accelerates the process of convective heat loss, as moving air replaces the warmer, stagnant air that clings to the body, thus promoting greater cooling effects. At lower speeds, such as those indicated in the other options, the effect on heat transfer is minimal, as the layer of heated air around the body remains largely undisturbed. This demonstrates the importance of understanding environmental factors in professions like firefighting, where such conditions can critically influence thermal stress and overall safety.