Weighing just 28 oz, Met One Model 831 provides data of 4 mass ranges (PM1, PM2.5, PM4, PM10) in one minute. Unit features 2 front-panel buttons that accompany rotary scroll wheel. Sample history is viewed on display or data may be exported via USB port using included software. Capable of storing up to 2,500 sample events, monitor operates on battery power for 24 hours of intermittent use and up to 8 hours of continuous use. Recharge time is 2.5 hours.