Kestrel Heat Stress meters are specially designed for fast and accurate measurement of the critical weather conditions that can cause serious and life-threatening heat stress injuries to employees, athletes, pets, and livestock. When exerting in a high heat environment, properly measuring conditions is crucial - Heat Stress meters measure Thermal Work Limit (TWL) and Wet Bulb Globe Temperature (WBGT), which is ambient temperature without the influence of air temperature, wind, and solar insulation.