Although they may be supplied as a high-pressure gas, most are shipped to the customer in a liquid state and vaporized on site. The primary cryogenics are O2, N2, Ar, H2 and He are supplied in much smaller quantities.
Cryogenic gases are purchased for their particular properties. They may be used as an inert blanket, in a chemical reaction or as a catalyst. Due to this usage, they are sold in various degrees of purity. Moisture (H20) is obviously an impurity, although on a very small scale. Moisture levels will, typically, be in the 0-5 PPM range.
Due to the purity of the gas and cleanliness of the application, there are few problems with this application. The sensor should be in a bypass after the vaporizer and not directly in the flow. This will warm the sample and ensure that the flow past the sensor is not excessive. Learn more on dew point measurement.