The oxygen content is an important parameter for monitoring processes. Among other things, explosive substances are often used in the production of pharmaceutical intermediates and active ingredients. To avoid explosions or degradation, the oxygen content must be monitored. Laser spectrometry using TDL (Tunable Diode Laser) is a time and cost-saving measurement technique. Typical processes in the pharmaceutical industry will be used to illustrate areas of application and case studies and provide solutions.