Project Sizing   Determine Your Drying Needs Desiccant Dehumidifiers work by taking wet air and processing it into dry air. This air exchange rate is measured in CFM (Cubic Feet per Minute). Therefore, to determine what size unit you need, you must first measure the building you wish to dry and convert it to CFM. 1. Calculate the cubic feet measurement of the affected area.Building Length X Building Width X Ceiling Height X Number of Floors EXAMPLE :  100ft x 40ft X 10ft X 1 Floor = 40,000 Cubic Feet 2. Determine how many air exchanges per hour are required for effective drying. Then multiple the cubic feet of the structure by the desired amount of air changes per hour - 2 to 3 is ideal. This will yield the cubic feet per hour of dry air that must be introduced to the building for desired drying to occur. EXAMPLE : 40,000 Cubic Feet X 3 Air Exchanges = 120,000 Cubic Feet 3. Divide the product by 60 to calculate the cubic feet per minute (CFM) required. EXAMPLE : 120,000 Cubic Feet / 60 Minutes = 2,000 CFM Use this number in conjunction with our rental catalog to determine which Desiccant Dehumidifier is right for you.