The properties of a double beam instrument make the PA-IR spectrometer the ideal device for infrared analysis on chemical processes that occur over a long time period. In just a few minutes the PAIR instrument can be set up to analyze a sample continuously for hours, days or weeks. With sample and reference constantly being monitored simultaneously, the negative effects of instrument drift are almost completely eliminated. Changing environmental conditions, instrument temperature changes and source fluctuations affect both the reference and sample channels simultaneously and are cancelled out. Whether studying a transient system or doing a long temporal study, our patented dual beam setup eliminates the need to ever purge the instrument with nitrogen or other inert gases.