Pharmaceutical plants sometimes need to cultivate batches of living organisms like the fungi that are use to make penicillin...and they need an optimum stable temperature and RH to produce the needed amount in the shortest time frame...
Plants that produce "plasma" TV screens have found that a high RH in the manufacturing environment results in early failures and are enclosing some phases of the manufacturing process in environmental chambers.
Computer chip manufacturers need a clean and stable temp/RH environment.
Archives and museums (where I was exposed to these systems) need those chambers to extend the life of paintings, film, and documents...
Usually in museums only a small percentage of their collection is out hanging in the galleries.... the majority is stored in vaults and the exhibitions are rotated to limit their time in harsher environments.
Each industry has different requirements, some warm and humid and others dry and cold.... but all have to be stable
with minimal fluctuation.
The HVAC manufacturers have environmental chambers where they have to certify the SEER ratings of their units(splits and package units) in differing simulated outdoor and indoor temperatures and humidities.... my first job with this company will be at an HVAC manufacturer (Hello Robo) installing chambers for SEER testing.
Lithium batteries require <than 2% rh worked on a system recently the condensing units actualy sit in a room that is the air handler.If you spend half a day in there it will make your throat burn.Very interesting system this one was r-22,oil seperators,oil reservoirs,and floats by ac&r just like a rack system,also has a dessicant wheel.I believe munters was the manufactuer,like the dry cool units on super wally world(the demise of the country once run by moms and pops everywhere)I hate walkmart.