A method for treating a biological fluid within a container, the biological fluid having a hematocrit, volume, weight, viscosity, density, and temperature and the container holding a volume of air, by subjecting the container to light using an apparatus including: i) a fluid treatment chamber for receiving the container of biological fluid, ii) an agitation assembly for oscillating the container of biological fluid within the fluid treatment chamber including a variable-speed motor, iii) one or more light sources in proximity to the container of biological fluid when placed within the fluid treatment chamber, and iv) one or more sensors for sensing a condition of one or more of the energy of the light emitted by the one or more light sources, the hematocrit of the biological fluid, the weight of the biological fluid, the volume of the biological fluid, the density of the biological fluid, and the temperature of the biological fluid, and the volume of air in the container, the method comprising: a) establishing a predetermined value for one or more of the energy of the light emitted by the one or more light sources, the hematocrit of the biological fluid, the weight of the biological fluid, the volume of the biological fluid, the density of the biological fluid, and the temperature of the biological fluid, and the volume of air in the container; b) placing the container of biological fluid in the fluid treatment chamber (step 100); c) selecting an initial oscillation rate for oscillating the container of biological fluid within the fluid treatment chamber (step 102); d) oscillating the container of biological fluid at the initial oscillation rate (step 106); e) activating the one or more light sources for emitting light energy (step 104); f) sensing one or more of the conditions of i) the energy of the light emitted by the one or more light sources, ii) the hematocrit of the biological fluid, iii) the weight of the biological fluid, iv) the volume of the biological fluid, v) the density of the biological fluid, vi) the temperature of the biological fluid, and vii) the volume of air in the container (step 108a); g) comparing the sensed values of the one or more conditions to the predetermined value for the same one or more conditions to determine any difference there between (step 112a); h) determining new oscillation rate (step 114a) and varying the speed of the motor to adjust the oscillation rate of the agitation assembly (step 116a) based on the difference between the predetermined value for the sensed condition and the sensed condition; wherein the steps of sensing one or more of the conditions (step 108a), comparing the sensed values of the one or more conditions to the predetermined value for the same one or more conditions (step 112a), determining new oscillation rate (step 114a) and varying the speed of the motor to adjust the oscillation rate of the agitation assembly (step 116a) are repeated periodically throughout the irradiation cycle, until the total amount of light energy to be delivered to the container has been achieved. a) establishing a predetermined value for one or more of the energy of the light emitted by the one or more light sources, the hematocrit of the biological fluid, the weight of the biological fluid, the volume of the biological fluid, the density of the biological fluid, and the temperature of the biological fluid, and the volume of air in the container; b) placing the container of biological fluid in the fluid treatment chamber (step 100); c) selecting an initial oscillation rate for oscillating the container of biological fluid within the fluid treatment chamber (step 102); d) oscillating the container of biological fluid at the initial oscillation rate (step 106); e) activating the one or more light sources for emitting light energy (step 104); f) sensing one or more of the conditions of i) the energy of the light emitted by the one or more light sources, ii) the hematocrit of the biological fluid, iii) the weight of the biological fluid, iv) the volume of the biological fluid, v) the density of the biological fluid, vi) the temperature of the biological fluid, and vii) the volume of air in the container (step 108a); g) comparing the sensed values of the one or more conditions to the predetermined value for the same one or more conditions to determine any difference there between (step 112a); h) determining new oscillation rate (step 114a) and varying the speed of the motor to adjust the oscillation rate of the agitation assembly (step 116a) based on the difference between the predetermined value for the sensed condition and the sensed condition;