Fan operation should be controlled by maintaining less than a 10 F difference between grain temperature and average outside air temperature. 2 shows that, in an average year, rice should be cooled to below 50 F by December. Improper aeration leads to mold development. Early signs of mold growth can be detected by smelling the first air that is exhausted from a storage after fans are turned on. Average air temperature in the Sacramento Valley.
Rice is cooled in fall, kept at low temperature in the winter and warmed in the spring.
Under many conditions, fans are operated about two times per week. Table 2 in the bin drying chapter describes the specific air temperatures and humidities suitable for aeration at given rice moistures. Humidity below a recommended range will over dry the rice and humidity above the range will raise rice moisture to unsafe levels. During fan operation air temperature should be cooler than the rice in the fall and warmer than the rice during late spring. Aeration controllers are available which will automatically start and stop fans based on grain and air temperatures and some also control on the basis of air humidity.