TM 10-3930-659-10 3-11.  CHECK AND CLEAN ENGINE PRIMARY AIR FILTER AND UNLOADER VALVE (Con’t). (2)  Loosen  wlngnut  (6)  and  remove  primary  air filter (5) from air cleaner housing (4).  Check air filter for damage or dirt. (3) Clean primary air filter (5) as shown. (4) Tap primary air filter (5) with palm of hand to remove dust. WARNING Compressed   air   used   for   cleaning   or   drying   purposes,   or   for clearing  restrictions,  should  never  exceed  30  psi  (207  kPa).    Wear protective clothing (goggles/shield, gloves, etc.) and use caution to avoid Injury to personnel. (b) Direct compressed air up and down pleats of air filter element, from inside to outside, to remove dirt from primary air filter (5). (4) Install primary air filter (5) in air cleaner housing (4) and tighten wingnut (6). (5)  Position  air  cleaner  cover  (2)  in  place  and secure with wingnut (1). b.  Clean Unloader Valve. Squeeze   unloader   valve   (3)   to   remove   dust   from   air cleaner. 3-18