Uses an active sensor technology with an internal fan to pull air across the GSE sensor at a specific flow rate for accurate gas detection. Designed to be a direct fit to any Aeroqual Series-500 Aeroqual ozone monitor. The Aeroqual Sensors are housed within an interchangeable ‘sensor head’ that attaches to the Aeroqual S500 Portable Air Quality Monitor base. You can choose from up to 30 different sensor heads. Each sensor contains a single gas or particle sensor. Swapping sensor heads takes seconds and no configuration or re-calibration is required.