attractive option because of their relative low cost compared to conventional silos. However, when fabric silos are used to store granular or particulate combustible materials, conventional practices prescribed by established industry consensus standards addressing combustible dust hazards can not be applied without a considerable engineering analysis of the system. History The 5th millennium BC site of Tel Tsaf in the southern Levant contain the earliest known silos. Archaeological ruins and ancient texts show that silos were used in ancient Greece as far back as the late 8th century BC; the term silo is derived from the Greek σιρός (siros), "pit for holding grain". The silo pit, as it has been termed, has been a favorite way of storing grain from time immemorial in Asia. In Turkey and Persia, insurance agents bought stores of wheat or barley whilst comparatively cheap, and store it in hidden pits against seasons of dearth. In Malta a relatively large stock of wheat was preserved in some hundreds of pits (silos) cut in the rock. A single silo stored from 60 to 80 tons of wheat, which, with proper precautions, kept in good condition for four years or more. The first modern silo, a wooden and upright one filled with grain, was invented and built in 1873 in Spring Grove, Illinois by Fred Hatch of McHenry County, Illinois, USA. Forage silo usage Forage harvesting Forage silo filling is performed using a forage harvester which may either be self-propelled with an engine and driver's cab, or towed behind a tractor that supplies power through a PTO. The harvester contains a drum-shaped series of cutting knives which shear the fibrous plant material into small pieces no more than an inch long, to facilitate mechanized blowing and transport via augers. The finely chopped plant material is then blown by the harvester into a forage wagon which contains an automatic unloading system. Tower filling Tower forage filling is typically performed with a silo blower which is a very large fan with paddle-shaped blades. Material is fed into a vibrating hopper and is pushed into the blower using a spinning spiral auger. There is commonly a water connection on the blower to add moisture to the plant matter being blown into the silo. The blower may be driven by an electric motor but it is more common to use a spare tractor instead. A large slow-moving conveyor chain underneath the silage