A new type of smaller and more compact process gas chromatograph (GC) is built with silicon wafer technology and modular design that provides the versatility of conventional process gas for many applications. The GC can be specifically applied to measurement of heating values. The design and its analytical abilities mean short analytical time and elimination of impact of sample pressure or ambient pressure variability on the accuracy of measurement. Users can routinely monitor analytical results, precision, and hardware performance, and also can see performance deviations and take action before failure. These are important criteria for analytical only reliability and measurement correctness. Maintenance is merely a matter of a fast exchange of modules. The online process GC benefits from the most current miniaturization techniques, including silica wafer technology and microelectromechanical systems (MEMS), and is designed for suitability in the environment, with not large infrastructure modifications required. A housing and three modules (analytical, pneumatic, and electronic) make up the analyzer, and each is standards-based for design, connectivity, interface, and swap-out. The three modules are in a small cast alloy housing so that they can be installed in a hazardous environment without purge requirements. The components of the GC and its operation are described in detail.