Inline filters are a really good idea to remove contaminants from air tools and moisture. You need to drain them periodically as well. Another good idea is put an in-line lubricator to increase the life of your air impact wrench. An in-lubricator lubricates your air tool as you are using it. You should pour some oil in it and run your air tool before storing it after use. Consult your manufacturer specs for the proper oil to use.