Diurnal growth chambers are designed for studies requiring day and nighttime simulation. This unit features dual-program selector dials, which allows control of two temperature conditions and an ON/OFF illumination cycle relative to the program selected. Each system operates independently allowing for simulation of a diurnal cycle, such as an eight hour day cycle of 30oC with light followed by a sixteen hour night cycle of 18oC without light. Forced air circulation ensures the most reproducible test conditions. The chamber air is gently and continuously circulated at a rate that ensures temperature uniformity of all test samples.