The Clean Air Board announced that it has installed a new air quality monitor in downtown Carlisle near the Square. The PM2.5 sensor will report its readings 24 hours a day. The real-time data can be viewed on the PurpleAir network. The PurpleAir™ sensor is a device that uses two laser particle counters to capture and record data about microscopic particulate matter (PM2.5) suspended in the air. The sensor uses WiFi connectivity to display real-time air quality readings on the PurpleAir™ Map, which is a world-wide map of monitors where data can be shared with the public.