I use a tier shelving unit 7ft high 2ft deep by 4 ft wide. Have a cover on it. 36 x 580rx. Air in it is 45c. Cards around 73c-80c and I have a 6inch duct grow op fan sucking air out of it. The smaller the cubic ft area you have, the quicker the air is changed. I looked at it like cubic ft area with cfm 440cfm ÷ (4x2x7=56) = 7.85 times per minute. Then divide 60 seconds by the result. 7.62 seconds air is totally changed in that area. I'm happy with it and it keeps everything cool. Just my cents 100w fan vs 1500w a.c.....