Which instrument is the basic tool for assessing heat stress?

• A. WBGT Meter
• B. Thermometer
• C. Hygrometer
• D. Anemometer

Answer: (B)

To assess heat stress effectively, you need an instrument that captures the full heat load a person experiences, including air temperature, humidity, radiant heat, and air movement. A WBGT meter does exactly that by measuring dry-bulb temperature (air temperature), wet-bulb temperature (which reflects humidity and evaporative cooling), and globe temperature (which accounts for radiant heat from the sun or surroundings). These three measurements are combined into the Wet-Bulb Globe Temperature index, which provides a practical assessment of heat stress risk and helps set work-rest cycles and safety precautions.

A plain thermometer only tells you the ambient air temperature. It misses humidity, radiant heat, and wind effects, all of which strongly influence how hot it feels and how the body dissipates heat. Humidity reduces evaporative cooling; radiant heat from sunlight or hot surfaces adds to the heat load; and wind can either remove or bring heat depending on conditions. Because of this, a thermometer alone cannot give a reliable heat-stress risk assessment.

A hygrometer measures humidity, which is useful but incomplete for heat stress on its own. An anemometer measures wind speed, which affects convective cooling but again does not provide the full picture without temperature and radiant heat data. The WBGT index incorporates all these factors into one practical metric, making it the best tool for assessing heat stress.