Multiple-blower relative humidity controlled test chamber

An accelerated weathering apparatus includes a test chamber, a specimen supporting means, a light source powered by a power source controlled by a ballast, at least one chamber air temperature sensor, a black panel temperature sensor, and a multiple blower system and control means. A first blower draws and circulates outside or fresh air and as second blower optionally draws recirculated air into an air mixing duct. The speeds of the fresh air and recirculated air blowers are independently regulated and controlled by a blower controller based on the chamber air temperature and black panel temperature, respectively. In addition, a humidifier and humidity controller regulates humidity within the system as required.