Question

Above which level of the heat stress index (HSI) is it not possible to work comfortably?

• A. 20 - 40
• B. 40 - 60
• C. 60 - 80
• D. 80 - 100

Hint:

Severe heat strain begins in the mid range of the index, not the highest band.

Answer 1

The Correct Option is B

Step 1: The heat stress index (HSI) expresses the heat load on the body as the ratio of the evaporative cooling required to the maximum evaporative capacity of the environment, scaled to a percentage.

Step 2: Low values reflect little strain, but as the index rises the body must sweat more to maintain thermal balance. An HSI in the range of 40 to 60 produces severe heat strain, at which point comfortable continuous work is no longer possible.

Step 3: Therefore the threshold asked for corresponds to option b, 40 to 60. Below this, work remains tolerable, while values still higher (60 to 80 and 80 to 100) represent extreme and potentially dangerous heat loads.

Step 4: So the correct answer is 40 to 60, the band marking severe strain beyond which comfortable work cannot be sustained.