TWL-1S Heat Stress Meter

The TWL is the thermal work limit. It’s an advanced heat stress index and research found it more useful in workplaces.

Yes. The TWL-1S has been tested and validated by the Health Authority – Abu Dhabi in extreme high temperature and humidity conditions in the Gulf region, as well as in Australian mining sites. Thermal Work Limit (TWL) algorithm used in the device is the latest version and has been attested by the research team at Curtin University, Australia.

Thermal Work Limit (TWL) predicts the maximum safe level of work that can be performed in a specific environment without exceeding a core body temperature of 38.2°C (100.8°F) or a sweat rate of 1.2 kg (2.6 lb) per hour. In contrast, Wet Bulb Globe Temperature (WBGT) does not incorporate a direct measure of wind speed and requires estimated metabolic rates, which can have a margin of error of up to 50%.

Additionally, heat stress indexes like WBGT and ISO 7933 do not factor in the effects of prolonged hard work, dehydration, or the impact of personal protective clothing and equipment. WBGT and the heat index are often too conservative and impractical for extreme environments such as the Middle East, high-temperature industrial processes, or mining operations.

Scarlet TWL-1S combines the features of both WBGT and TWL indexes, allowing you to easily switch between heat indices based on your needs.

TWL-1S is ideal for assessing heat-related illness risks in high-temperature environments. Health and safety officers can place the device at “hot spot” zones to continuously monitor environmental conditions.

Because factors like humidity and sun exposure significantly affect how hot your body actually feels. A heat stress meter accounts for all of these, providing a more accurate assessment of environmental heat risk

Since TWL mimics the working environment’s impact on laborers, TWL-1S unit should be placed where most workers are located. For example, if the worksite lacks shade, TWL-1S should be in direct sunlight to reflect actual conditions.

To extend the device’s life, you can keep it in the shade when not measuring. While measuring, place TWL-1S in sunlight and let it stabilize for at least 10 minutes before pressing the TWL button. Once TWL level appears, you can return it to the shade.