Such a compressor should NOT be used for hydrogen. There are many issues with converting a compressor to hydrogen service. First and most important, this must be approved by the manufacturer. Examples of concerns for a non-hydrogen compressor used for hydrogen service include (but are not limited to): 

1. Are the materials compatible with hydrogen permeation, embrittlement, hydrogen corrosion stress cracking, etc.?
2. How much hydrogen gases can migrate past seals on the pump? Is this blow-by captured to a safe location that is compatible with hydrogen?
3. Are the electrical controls classified for hydrogen service, such as Class 1, Division 2, Group B?
4. Seal materials, compression ratios, and cylinder temperatures are not likely to be compatible for hydrogen.
5. Are the mechanical portions of the compressor suitable for H2 service, e.g., ignition sources such as hot surfaces?
6. Are enclosures within the machine or external to the machine suitable to safely address H2 accumulation?

If the compressor is a centrifugal, the molecular weight difference will not permit the machine to function.