Regional purging flow rate

Peng, S. H., Davidson, L, Towards the determination of regional purging flow rate. Build. Environ., vol. 32, pp. 513-525, 1997. 

TABLE 11.3 The Purging Flow Rate for the Six Regions Defined in Fig. 11.14 ... 

It is common to purge the air from the sample chamber owing to the relatively complex composition of the air and the fact that air contains a large proportion of highly interactive water vapour. The region of the microbalance mechanism should be constantly maintained under an inert, flowing atmosphere such as dry He or dry N2, even when the thermobalance is not in use. A flow rate of 30-40 ml/min is... 

The presence of carbon dioxide is usually not quite as detrimental as water vapor because CO2 absorbs in less important spectral regions for most applications. Nonetheless, the best spectra are acquired by purging the instrument with C02-free air. Some regenerating driers produce C02-free air. The flow rate of the purge gas through the spectrometer should be enough to reduce the level of H2O and CO2 to an acceptably low level within about a minute after the sample has been loaded into the spectrometer. However, the flow rate should not be too high, because microphonic noise can be introduced into the spectrum. 

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