HIGH PRESSURE PROBLEMS
Although raising the pressure of the sample puts more molecules in the light path and therefore might be expected to boost measurement sensitivity, the high pressure also causes problems. One problem is that if you are working with a humid sample, the water will condense during pressurization, fouling the absorption cell and possibly dissolving some of the trace gases in the sample. Another problem of high pressure is that the absorption lines and bands become broadened by the pressure and lose some of their distinctive characteristics. Also, excess pressure might blow up the absorption cell. It is best to work at a total pressure of one atmosphere.