For our storage rooms we use  two Honeywell  units with compressor pumps,  to filter and dry the air.   I once read an article that military standards require dried air for storage, and started to looks for something not so military, but good enough still.

When we first installed  the equipment, we needed to empty the water containers daily!  Although these rooms are in a  new building,  and feel not humid at all,  it was still amazing  how much water was obviously stored inside everything.

After installation the compressors ran 50% af the time,  but after four weeks, they started running less and less. Now they are normally off,  and only switch on occaisionally when the doors  were opened.  All paper and boxes are now crispy dry.

The military are right!  This is the best way to keep the high voltage materials, tubes, transformers and capacitors in good condition.