Access to clean water is critical for life. Physical Sciences Inc. (PSI) is currently developing a sorbent-based system for atmospheric water harvesting capable of providing drinking water in a man-portable configuration. To keep up with the high volume of sorbent development, PSI designed a rapid screening technique to evaluate the water uptake kinetics and overall capacity of these novel sorbent materials. This flow system inoculates a dry air feed with a high relative humidity (RH) consistently remaining between 90-95% RH. This sorbent screening tool was built using low-cost commercially available parts. The system went through multiple iterations to overcome challenges arising due to vapor condensation in the tubing, requirements for increased throughput, and achieving flow consistency though multiple beds. The resulting system produces repeatable results and has proved to be a vital tool in sorbent screening for PSI’s applications. This presentation describes the design process of the high RH flow system and operational validation. The application of this dynamic flow system is critical to our sorbent screening and was used to design our next generation atmospheric water harvesting system.