TM 10-8415-209-10 TM 8415-10/2 a. Chemical Protective Underwear Two-piece (CPU ).  The CPU is a two piece undergarment intended to be worn  under  the  standard  duty  uniform.    It  provides  chemical  protection  as  an  alternative  to  the  Battle  Dress Overgarment (BDO) in all climatic categories (hot, basic, cold, extreme cold).  The CPU is designed to be worn next to skin for up to 15 continuous days, and can be laundered once in its service life (see paragraph 3-2 for laundering procedures).  The CPU protection may be degraded by gross contamination with petroleum, oils, lubricants (POLs). The   CPU   will   be   issued   as   individual   equipment   to   certain   combat   vehicle   crewman,   aviators,   and   Special Operations units.  Refer to FM 3-4/FMFM 11-9 for protective capabilities. 1-13