The Federal Clean Air Act (FCAA) requires the U.S. EPA to set national ambient air quality standards to ensure public health. State agencies, as well as regional and metropolitan air quality management districts are responsible for ensuring attainment and maintenance of these standards.

These agencies have published rules and regulations regarding NOx and CO emissions from industrial, institutional and commercial boilers, steam generators and process heaters.

Owners or operators of units subject to these regulations may install a non-resetting totalizing fuel flow meter (TFF) to measure the total of each fuel used by each individual unit. The regulations specify mass flow measurement of fuel usage and if a volumetric flow meter is installed it must compensate for pressure and temperature using integral gauges. Thermal mass flow meters deliver a direct reading of mass flow rate of natural gas and other fuel gases — without temperature and pressure compensation — and provide a simple, reliable and cost-effective method for tracking and reporting fuel consumption.