We have been using Air Liquide Instrument Grade Air for venting the 40m vacuum envelope. It is no longer available.
The replacement is Alphagas 1, total hydrocarbon <0.1% ppm
LINK TO Alphagaz
Air Liquide > ALPHAGAZ™ Specifications
Because each analytical application is sensitive to critical impurities that can affect your results, tests in our research center and analyzer manufacturers' studies confirm that the main impurities are moisture, oxygen and hydrocarbons.
Based on these critical impurities, Air Liquide has developed ALPHAGAZ™ brand with a Maximum Impurity Level (H2O, O2, CnHm).