At the very least, keep a window open or you'll think your in a greenhouse. Tested mine out in the shop at home, completely enclosed. Walked back in there and it felt like a jungle, LOL. I use a MasterCool at work, the small unit. It is alright as long as it's blowin on ya directly. 100* + where I work. The higher the humidity in the day = less effective cooling. When the humidity is less than 50% it'll cool the heck out of ya. I go thru about 15 gallons of water in a 10 hour shift. Freeze some gallon milk jugs and add it to it and it rocks. In 3 years I have had to replace the motor and water pump.