I had a conversation with my Thermoking factory rep about refer units on trucks. There is NO humidity controls available. If you did add a humidifier, it would just be fighting the refer unit since one of the things the refer unit does is dehumidify the air. If you want temp control between 65-75 degrees without humidity control, that is not a problem. And you don't have to worry about hot or cold spots since the refer units push alot of air around the inside of the truck. Good Luck, TomC
I suppose they don't make mobile swamp coolers .