Executive summary Differential pressure (ΔP) measurement sits at the intersection of energy, IAQ, compliance, and reliability  in HVAC. It’s used for filter loading, duct static pressure, airflow inference, fan performance, and room pressurization (cleanrooms / isolation rooms). Three types of sensor dominate the market: Mechanical gauges : lowest cost and simplest deployment, but usually local-only  visibility unless you add switches or manual rounds. Wired electronic transm