Because the hot air of each circle is filtered through sub - high or high efficiency filter , it can avoid effectively that the carded raw material in the air is deteriouated and polluted during the period of re - circle and re - heating 热风每一循环均通过亚高效或高效过滤器过滤,能有效避免空气中夹带物料在循环再加热过程发生变质,对药品的污染。