Kind of defeats the purpose...BUT. I ran a test with one of the CO2 monitors in my tent with a block of dry ice. I had something shipped to me on ice so I figured I would throw it in the tent and see how much it actually produced. I left the fan on but turned it down to it's lowest setting. The ppm got up to 3700 after about an hour around 1:00pm. It dropped over the day and just about 10:30pm it was down to 910 and the ice had evaporated completely. I would think if you keep it on low and monitor the numbers it would be fine.