Re: small room humidifier
Maybe my room/humidifier just failed, but my experience using just a small regular humidifier (the size recommended for my room size) from the store didn't really result in a significant increase in room humidity. you may need one of the larger ones for a space much larger than the room you are planning to put it in if you're looking for an increase significant enough for your creatures.
But thats just my experience, so don't take it as law. I would suggest maybe working on the habitats specifically for humidity unless the dry air is bothering you as well.
Re: small room humidifier
I am having the same issues, I have my racks in a large walk-in closet in my room and need a space heater to keep the temps up. I have a good size humidifier in the room, but have noticed little change without spraying the cypress mulch every once in awhile. I am going to invest in a larger humidifier and hope for the best!!