American Solar, Inc. has developed an effective, low-cost solar air heating system based on mass-produced components that are readily available within the United States of America. The system collector and plenum is made of polymeric twinwall sheeting; the system fittings and corrugated duct are plastic. Sealing of the air heater system is achieved with silicone and various fasteners. Air movement is achieved by an assortment of inline, axial blowers. The collectors are modular and can be combined in parallel for multiple configurations. Since the air flow for the collector, fittings and duct had not been characterised, system specification had been inexact. This thesis explains how air flow characterization of the system was achieved. First, axial blowers and single and multi-collector system configurations were specified based on estimated volumetric flow requirements. Second, the various configurations were tested while attached to the specified blowers, and the associated performance data was recorded using an iris damper attached to a differential pressure sensor and a data logger. Third, the resulting performance data was analyzed graphically to determine the characteristic curves of individual components and configurations. Fourth, experimental conclusions were compared to theoretical predictions and available data for similar products to check for consistency. Finally, a design database of configurations with defined working points was created. Background, method, results, and analyses are presented.