There are many materials that can be used to make compressed air filters, which are mainly divided into the following five categories: 1. Fiber filter materials - such as cotton, wool, silk, etc. in natural fibers, glass fibers and chemical synthetic fibers in man-made fibers (polyester, polypropylene, etc.); 2. Filter paper; 3. Powder metallurgy materials - mainly include sintered bronze, sintered stainless steel and Monel alloy; 4. Filter ceramics - mainly quartz, alumina and diatomaceous earth; 5. Adsorbents of activated carbon. In the sub-high efficiency and Taiwan DPC high-efficiency precision filters, the first two types of filter materials are commonly used, and the latter filter materials are used in coarse-efficiency, medium-efficiency filters and some special industries.