Lisa, I have used stand-alone dehumidifiers in many situations over the years, generally with success equal to that of a purpose-built archival temperature and humidity control system. In every case, the machines operated according to their specifications, at least pertaining to the capacity to remove a certain amount of moisture from the air in a twenty-four hour period. The controls on various units were of variable quality, even when settings and readouts showed precise, digital figures (those may inspire confidence, but the actual sensors may be of only average quality). Some units provided a vague dial adjustment, yet overall, I found any of these to be of equal utility. Monitoring the surrounding air for relative humidity levels was the only way to ensure that our goals were being met, and it enabled us to fine-tune the settings on any of the dehumidifiers.
As to specific brands, I think that may be beside to point overall, since many machines -- especially the smaller ones -- are made in the same factories, but sold under various brand names. Still, machines made by Oasis, Dayton, and Dri-Eaz have worked well for me; most of these are termed "industrial", have quite large capacities, and are relatively costly. All that I purchased worked well, and for years on end.
Please contact me directly, if I may be of further help in this matter.
Bruce
A. B. MacLeish
Curator Emeritus, Newport Restoration Foundation
(H) 607-547-5172
(C) 401-265-8607