lines and leave drain open until all water is drained, then close drain. 2-19.  Operation in Extreme Heat a. General.        Refer    to    TM    9-2320-209-10    for additional   information   on   operating   the   fire   truck   in extreme heat.  Pumps are not affected by extreme heat, except for lubrication requirements. b. Lubrication-.    Be  sure  to  use  the  proper  grade lubricant  for  all  points  of  application.    Refer  to  LO  9- 2320-23-12  and  LO  -421021-12  for  special  lubrication. Check the lubricant level frequently. 2-20.  Operation in Sandy or Dusty Areas a. Lubrication.    Keep  all  lubrication  points  clean and   well   lubricated.      Lubricate   sparingly   but   more frequently than under normal conditions.  Clean all oily or  grease  surfaces,  paying  particular  attention  to  the pump oil fill as it accumulates dust and sand.  Service the    air    cleaners,    breathers,    and    oil    filters    more frequently than under normal conditions (TM 92320-209- 10). b. Cooling    and    Fuel    Systems.        Service    the radiator, fuel tank, and fuel filter (TM 92320-209-10). c. Pumps    and    Hose    Reels.        Keep    the    body compartment doors closed except to perform necessary operations.    Wipe  the  hose  reel  drive  gears  and  drive chains   to   remove   as   much   grease   and   oil   from   the exposed  surfaces  as  possible.    When  dusty  or  sandy conditions no longer exist, remove the chains and wash with    an    approved    cleaning    solvent,    lubricate    and reinstall.    Clean  all  the  machine  surfaces  of  the  pump and  control  linkages  to  remove  accumulated  dust  and sand. d. Electrical     Systems.          Keep     the     insulation electrical connections, and all motors free from dust and sand to prevent wear and short circuits.  Cover the siren when not in use. 2-21.  Operation Under Rainy or Humid Conditions a. General.    High  humidity  causes  a  rusting  and corrosive     action     to     exposed     metal     surfaces     not protected with oil or grease. b. Fuel  System.    Keep  the  fuel  tank  as  full  as possible to eliminate condensation.  Clean the fuel line sediment bowl daily (TM 9-2320-209-10) . c. Electrical Systems.  Keep the electrical system clean  and  dry.    Wipe  off  any  excess  moisture.    Pay particular attention to electrical connections. 2-22.  Operation in Salt Water a. General.      The   deterioration   and   corrosion   of exposed metal is greatly accelerated in salt water areas. Coat   all   exposed   metal   surfaces   with   an   approved! lubricant.  When the fire truck has been partly immersed or sprayed with salt water, wash down with fresh water. b. Pumping  Salt  Water.    Do  not  use  salt  water except  in  case  of  extreme  emergency.    At  the  earliest opportunity   after   pumping   salt   water,   flush   the   tank piping and fire pump thoroughly with fresh water.  After flushing, drain the fire pump. 2-23.  Operation at High Altitude a. General.    Operation  at  high  altitude  presents special problems due to lower atmospheric pressure and a  wide  difference  in  temperature,  which  occurs  during the day and night.  Protect the fire truck at all times from the lowest anticipated temperature. b. Cooling System.  Keep the cooling system clean and  filled  to  the  proper  level.    Inspect  frequently  as water  evaporates  more  rapidly  at  high  altitudes.    Keep the  radiator  clean  and  engine  compartment  doors  and radiator shutters open when in operation. Section V.  OPERATION OF AUXILIARY MATERIAL USED IN CONJUNCTION WITH FIRE TRUCK 2-24.  Fire Extinguishers a. All Fire Extinguishers on the truck are Government furnished equipment. b. Refer to TM 5-687 for maintenance and refilling. 2-24