Pharmaceuticals and Specialty Chemicals are typically produced in batches by mixing several components in a reactor. These reactors vary in size from table-top glass jars to large stainless steel or glass lined vessels with a mixer (like a giant domestic food blender). The vessel will be subjected to a nitrogen blanket prior to and during batch production so oxygen levels must be monitored at all times for plant and operator safety.
Previously companies used to permanently feed N2 to the process and not worry about the oxygen level. However, N2 is a consumable with an associated cost that can and should be limited. This is achieved by monitoring the oxygen level and shutting the N2 feed when the O2 levels are safe.
There are generally solvents or powders present in the reactor which could create an explosive atmosphere. In order to prevent explosions, the process is blanketed by nitrogen to ensure the Minimum Oxygen Concentration (MOC), of the particular solvent vapor, is not reached. The signal from the oxygen analyzer/system will be used to control the flow of N2 and/or shut the plant down. A loss of flow of N2 will be detected as the O2 level raises and the analyzer will trigger an alarm, preventing a potentially dangerous scenario. Portable analyzers such as the GPR-2000 ATEX are excellent for spot checking multiple vessels during maintenance.