One of the two factors used to determine the heat stress index?

• A. Apparent temperature
• B. Relative humidity
• C. Wind chill
• D. Duration of exposure

Answer: (B)

Heat stress index is determined by how hot it feels based on two environmental inputs: air temperature and relative humidity. Relative humidity matters because when the air is moist, sweat doesn’t evaporate as efficiently, making it harder for the body to cool itself and causing the perceived heat to be higher. That’s why relative humidity is one of the factors used to calculate the heat stress index. The other input is air temperature, which, combined with humidity, sets the overall heat load. Other options don’t feed into the index: apparent temperature is a broader “feels-like” measure, wind chill relates to cold conditions, and duration of exposure affects risk but not the index calculation itself.