smo,
To reduce moisture to a specific level you could try a hygrometer (humidistat) controlled dehumidifier with an outlet fitted to a drain.
The necessary rating of the dehumidifier depends on the volume of your data center, frequency or air exchanges etc.
Then you may occasionally need to add moisture to the air depending on where the data center is based.
For this you’ll need to consult with an HVAC engineer:
http://www.apc.com/salestools/NRAN-5TV85S/NRAN-5TV85S_R3_EN.pdf
Best wishes,
John