Oncidium-type plants are really tough. If your plants have been neglected for years, it's probably a good idea to take them out of their pots, remove anything that's dead or rotten, and repot into the smallest possible pot. Everybody has their own favorite medium. I use a mixture of small bark, perlite and charcoal. You can also use a mix of sphag and perlite, you just have to make sure that you wait until the medium is dried out before watering again. Humidity trays don't do very much except a few inches from the tray. If you have very dry air, a small room humidifier as suggested by Slipperfan would be much more effective. You can get one at any box store. The frustrating thing is that you probably won't see much improvement until the plants put out new growth. Good luck!
oke: but maybe it would be a way for her to go. They do not cost much (let me qualify that) if you build it yourself or start with some cheep shelving. It might be less costly then trying to humidify the whole space and it could advert the health issue.
