NOTE:   Remember   you   are   dealing   with   high- -pressure   gas.   Before   attempting   to   recharge   any extinguisher,    you    should    become    thoroughly acquainted   with   the   recharging   pump   and   the methods  of  recharging.  Carefully  read  the  instruc- tions   that   pertain   to   the   recharge   pump   and   be sure  all  connections  are  tight  at  all  times. C O₂ CYLINDERS   AND   SAFETY   DISC Carbon   dioxide   cylinders   should   be   charged with   “bone-dry”   carbon   dioxide.   Extreme   care must   be   taken   in   the   charging,   weighing,   sealing, and   testing   of   cylinders. The   safety   discs   of   the   cylinders   are   painted various  colors  to  identify  the  pressure  at  which they   will   rupture.   The   correct   color   disc   must   be used   in   every   case.   All   cylinders   are   manufactured in   accordance   with   the   requirements   of   the Interstate   Commerce   Commission   (ICC)   as   set d o w n    b y    t h e    B u r e a u    o f    E x p l o s i v e s .    T h e s e requirements   specify   that   the   cylinder   be   tested to   five-thirds   of   its   normal   working   pressure   and that   the   normal   working   pressure   be   stamped   on the   cylinder   immediately   following   the   letters ICC3A.   We   refer   to   this   procedure   as   hydrostatic testing.   Common   cylinder   stampings   and   the corresponding   test   pressures   are   as   follows: Cylinder Test Color   of Stamping Pressure Permissible   Disc ICC  3 3000 psi White ICC  3A  1800 3000 psi White ICC  3A  2015 3360 psi White ICC  3A  2205 3680 psi White   or   red ICC  3A  2300 3840 psi White   or   red You   should   never   use   a   disc   in   a   valve   where it   would   be   working   in   connection   with   a   different type   of   safety   disc   retainer.   Never   trim   a   safety disc   to   fit   a   valve   other   than   the   one   for   which it   was   intended. You   will   find   similar   markings   on   the   shoulder of   every   cylinder. ICC   3A   1800 W.  K.  &  Co. 221974 10-84 H An   explanation   of   these   marks   follows: ICC  3A  1800  signifies  the  specific  ICC  test procedure   followed.   The   number   1800   indicates the   service   pressure. 221974   is   the   cylinder   serial   number.   Some cylinders   have   one   or   two   letters   as   part   of   the serial   number.   (The   U.S.   Navy   also   assigns   one of   their   numbers   to   all   cylinders   they   purchase. This  number  has  the  letters  USN  accompanying it.)  The  letter  H  in  a  shield  is  the  designation  mark of  the  accredited  ICC  inspecting  laboratory  that supervises   our   tests. The  letters  W.  K.  &  Co  designate  the  manufac- turer   of   the   cylinder. The   numbers   10-84   mean   that   the   cylinder   was tested   in   October   of   1984   and   that   its   next   test will   be   October   1989. Before   any   cylinder   is   recharged,   the   date   must be   checked;   if   more   than   5   years   has   elapsed,   the cylinder   must   be   retested   hydrostatically.   The date  of  the  retest  is  then  stamped  on  the  cylinder directly  under  the  original  date.  This  new  date  is the   one   against   which   future   checks   should   be made. Remember   you   are   dealing   with   high-pressure gas.   Before   recharging   any   cylinder,   you   must become   thoroughly   familiar   with   the   proper procedure    for    recharging. When   you   handle   or   ship   cylinders,   the shipping   cap   should   always   be   assembled   on   the cylinder.   On   cylinders   where   this   is   not   possible, the   cylinder   should   be   carefully   crated. Be   thoroughly   familiar   with   these   procedures before   you   attempt   to   recharge   any   cylinder.   A few   minutes   spent   on   becoming   familiar   with   the procedure   may   prevent   an   accident   involving injury   to   personnel   or   damage   to   equipment. WINTERIZING   CARBON DIOXIDE   CYLINDERS The   PR   is   not   normally   tasked   with   the responsibility   of   recharging   fire   extinguishers   and engine   fire   bottles. H o w e v e r ,    y o u    m a y    be assigned  to  an  AIMD  that  supports  aircraft  that require   winterizing   of   CO₂ cylinders. All   carbon   dioxide   portable   fire   extinguishers installed   in   aircraft   and   all   aircraft   carbon dioxide   built-in   engine   fire   extinguishers   are serviced   to   operate   throughout   the   temperature range  of  –65°F  to  160°F.  The  extinguishers  are supercharged  with  the  addition  of  200  psi  of  dry, oil-free   nitrogen.   This   servicing   of   extinguishers is   done   in   connection   with   the   U.S.   Air   Force winterization   program.   Extinguishers   charged   to meet    this    winterization    requirement    are    identified by   a   yellow   dot,   three-fourths   of   an   inch   in diameter   or   larger,   on   opposite   sides   of   the cylinder.   Extinguishers   so   marked   are   winterized 3-11