The PM150 Series CARBON DIOXIDE GAS MONITOR is low maintenance, rechargeable, and has an easy-to-read LCD display. It continuously monitors ambient air conditions and provides real-time carbon dioxide concentrations. It uses a three-tier alarm system with audible, visual, and vibration alarms when carbon dioxide levels are unsafe. The low, high, STEL, and TWA alarms can all be adjusted with the USB charge and software.