appropriate  chemical  tests  fail  to  give  a  positive response for a residual agent. Decontamination at naval shipyards, advanced bases, or by shore-based personnel will normally be of the 100% chemically complete type. This level is  not  mission essential for shipboard units. DECONTAMINATION OF THE SHIP The purpose of decontamination is to remove or reduce CBR contamination so that the ship can carry out its mission without danger to the life or health of its crew. Each type of contamination requires different decontamination  procedures.  Radiological  (nuclear) contamination may be removed by washing it over the side; CW agents may be neutralized; BW agents must be destroyed. Nuclear Radiation Decontamination Complete  decontamination  of  a  ship  usually requires the service of a shipyard. However, radiation levels can be reduced by shipboard personnel to the point  where  radiation  no  longer  presents  a  serious hazard to the crew. Most of the radioactive particles can be removed by washing down the ship. Two washdown methods are used—mechanical and manual. MECHANICAL  METHOD.—The  mechanical method,  called  the    ship’s  water  washdown  system, consists of a system of piping and nozzles that spray water over all weather surfaces. Water is supplied by the fire main. NOTE The washdown system actually is a preventive measure  against  fallout,  rather  than  a decontamination method, because normally the system is activated before the ship enters the fallout area. The  water  spray  carries  away  the  radioactive particles as they fall on the ship. At the same time, the flowing water fills in the cracks and crevices so that the particles that do get through the spray cannot settle into the cracks and crevices. MANUAL METHOD.—If parts of the ship are contaminated before the washdown system is turned on, water from the sprinklers may not effectively reduce the radioactivity because the slowly flowing water doesn’t have enough force to wash away the particles. The areas of heavy contamination must be hosed down with water under pressure. Hosing and scrubbing down the ship is the manual method. Decontamination teams are formed to hose and scrub down the ship. A team usually consists of six people—the monitor, who is in charge; two hosemen; and  three  other  team  members.  The  hosemen  wash down the hot spots with fire hoses, moving from the areas  of  less  contamination  toward  areas  of  greater contamination, and working from top to bottom. Then the areas are scrubbed by the remaining team members with soap or detergent and water and are rinsed by hosing  (fig.  13-11).  The  hosing-scrubbing-hosing continues until monitoring shows that contamination is removed or at least reduced to a safe level. Keep the contaminated water away from vent systems, doors, and hatches, because washing away the particles does not destroy them; they are simply being moved over the side. BW and CW Decontamination BW  decontamination    means  eliminating  the sources of infection. Using a chemical disinfectant is the most effective way to decontaminate BW agents. The  type  of  disinfectant  depends  on  the  agent,  the material to be decontaminated, and sometimes the area. Other methods include burning, dry heat, and moist heat.  Burning  usually  is  unsatisfactory  because  it naturally destroys surface material. An example of dry heat is a hot air oven set at 180E   . Moist heat includes hot water or steam under pressure. Sunlight also is effective in reducing BW contamination. The ultraviolet rays of the sun kill most BW agents. In   CW  decontamination,  weather  alone  is  the simplest means. Bright sunlight is a decontaminant, even  in  cold  weather.  However,  lack  of  time, unfavorable weather, or contamination of critical areas may require a faster method. Enclosed spaces can be steamed.  All  spaces  can  be  treated  with  liquid detergents.  Water  alone  is  often  satisfactory  as  a flushing agent; hot water or steam is better than cold water. 13-24 Student Notes: