The IMx Monitoring system is a highly modular Fourier Transform Infrared (FTIR) monitor that can be configured by the user to perform one of several different monitoring tasks. The IMx consists of a base unit and snap-on accessories. The accessories allow for A. extractive monitoring (e.g. stack or process control) using one of several different cell configurations or B. open path monitoring (e.g. cross-stack or open-air) using telescope based accessories. All units are NEMA enclosed for use outdoors or in explosive environments and configurations exist for internal or external computer control.