Which statement about heat stress factors is true?

• A. High ambient temperature, low wind velocity, and high humidity contribute to heat stress
• B. Only high ambient temperature matters
• C. Wind velocity has no effect on heat stress
• D. Humidity is not a factor

Answer: (A)

Heat stress occurs when the body's cooling mechanisms can’t keep up with environmental heat load, which is shaped by temperature, humidity, and air movement. High ambient temperature adds to the heat the body must dissipate. High humidity makes sweat evaporation less effective, so cooling is impaired. Wind velocity matters because moving air enhances convective heat loss and sweat evaporation; when wind is low, cooling is reduced. Therefore, the combination of high temperature, high humidity, and low wind creates the greatest heat stress. The other statements ignore the roles of humidity or wind and are not accurate. In practice, heat-stress assessment often uses measures that incorporate temperature, humidity, wind, and radiant heat to gauge risk.