methods of and systems for preventing air pollution in the handling and storing of particulate solids out - of - doors in bulk form ; i . e ., in a pile . a windfoil arrangement keeps material from being entrained in wind blowing over the pile and thereby causing an air pollution problem . the problem is particularly acute when material is being dumped ; it also arises when wind strips the particulate material from the pile , and it can result in the particulate material being scattered over a widespread area which indicates that the air pollution is not restricted to the immediate vicinity of the area in which the material is stored .