Recent updates to U.S. EPA NESHAP regulations have made fenceline monitoring a core compliance requirement for many chemical manufacturing and refinery facilities. Facilities must now track hazardous air pollutants at their site boundaries, respond quickly to exceedances, and maintain detailed records and quarterly reporting. This application note outlines the regulatory drivers behind these requirements and explains how continuous, real-time monitoring and integrated cloud workflows can replace delayed passive methods with faster detection, reliable source attribution, and more defensible compliance.