ddubridge:I think the bottom of the humidifier is a water cartridge which I dont think is a sealed unit. I wouldnt think you could lay it on it's side. You could always email a rep for clarification on the model you are intrested in.
Also, I think there is smaller models of this type of humidifier. Seems like this might be over kill for your humidor if it wont fit standing up. (3.4 inches tall) This model is meant to humidify 8 cubic feet.
Guess I was a little late on the answer.
Rammer13:My humidor is a 300 count multi shelf and layer humidor. Its not 8 cubic feet, but close. I have been having humidity problems and not being able to keep the humidity up. Any suggestions?