Multi-function instrument shows all ranges of dangerous heat conditions. Easy to adjust audible warning sounds before heat index reaches critical level. Accurate temperature, relative humidity, and heat index is always shown on easy to read display. Critical information is stored in memory for 24 hours and can be redisplayed. Also functions as stopwatch, countdown timer, calendar, & alarm. Rugged ergonomic design fits in the palm of your hand. Includes lanyard and soft carry case. Powered by single wafer battery.