1. A method of evaluating degradation of an air separation module tubesheet, the method comprising: subjecting the air separation module tubesheet to infrared spectroscopy by exposing the air separation module tubesheet to a spectrum of infrared radiation and collecting a spectrum of return signals; providing a regression model based upon a multivariate regression of a representation of the infrared spectra collected from a plurality of air separation module tubesheet samples having different predefined conditions; and determining a condition of the air separation module tubesheet based upon a representation of the spectrum collected from the air separation module tubesheet and the regression model.