Heat stress results from a combination of environmental factors, including air temperature, air flow, humidity, and radiant. This yellow Kestrel 4400 Heat Stress Meter features natural wet bulb temperature, black globe temperature, thermal work limit, on-screen alarms, and clothing level customization. From training soldiers to training athletes, the Kestrel 4400 will assist in preventing heat illness. Kestrel 4600 Heat Stress Meter 0846