Abstract: A portable gas analyzer includes multiple docking stations connected to a pneumatic flowpath through the gas analyzer. Modules are removably mounted to the docking stations. Some modules can be mounted at any one of the docking stations. The modules can include gas sensors and a microcontroller configured to generate data based on signals generated by the gas sensors. The modules are configured to simultaneously form each of electrical, mechanical, and pneumatic connections with the gas analyzer when mounted to the docking station.