A few days ago I added two more fans to my orchidarium. I was having problems with spotting on the leaves of some Masdevallias, and I have always been a believer in air movement - good air movement solves most problems with leaf drop and spotting if the humidity is high enough. I added them at the top of the case near the front sliding panels and they already seem to be making a difference. The case badly needed cleaning and I was able to combine the addition of the fans with a thorough cleaning, something I do two or three times a year.
This makes a total of six fans in the case. Four three-inch fans provide air movement and two four-inch fans blow down into the water at the bottom of the case and provide both air movement and humidity. The humidity in the case never goes below about 70 percent and rises to about 90 percent after watering. With the air movement, the humidity and the cool temperatures the environment seems to be about as good as I can make it for Pleurothallids and New Guinea Dendrobiums.
Someone asked if I would post some pictures of the plants and flowers in the case. That was a tough assignment, since the combination of harsh light, dark and light subjects, and air movement made it difficult to get decent pictures. These were the best I could do and I apologize for the poor quality of the pictures.