Thermal mass flowmeters with Modbus I/O are available for line sizes ranging from ¼ in (6 mm) to large stacks and ducts. They measure the flow of air and more than 200 different gases, including inert and hydrocarbon-based, in both pure and mixed compositions. Thermal mass air/gas flowmeters are direct mass flow-measuring, have no moving parts to foul or clog and require no routine maintenance. They range from small, compact models to high-feature, high-performance, high-accuracy models. Some models carry global agency approvals for Ex installations, both Div. 1/Zone1 and Div. 2/Zone 2 types. Four of the series carry independently evaluated SIL compliance (IEC 61508) ratings.