Meeting today’s fenceline monitoring requirements under the HON, RSR, and CMAS rules requires more than periodic sampling—it requires timely insight, rapid source identification, and efficient compliance workflows. This application note compares active and passive fenceline monitoring approaches, highlighting differences in data frequency, detection speed, operational burden, and long-term cost. It outlines how real-time active monitoring can support faster response, improved compliance confidence, and greater operational efficiency compared to traditional passive methods.