Principles of naval engineering - Historic Naval Ships Association

Chapter 4-PREVENTIVE ANfD CORRECTIVE DAMAGE CONTROLclothing, which includes a parka, trousers,rubber boots, and gloves, is easily decontaminated.Ordinary work clothing (including long underwear,field socks, coverall, field boots, andwatcli cap) is partially effective in preventingdroplets of liquid chemical agents and vaporsfrom reaching the skin. However, ordinary workclothing is not as effective as the other typesof clothing in preventing contamination. Undersome conditions, personnel may wear two layersof ordinary work clothing to achieve greaterprotection than can be obtained with one layer.PROTECTIVE MASKSThe protective mask is a very importantitem of protective equipment, since it protectssuch vulnerable areas as the eyes, the face, andthe respiratory tract. The protective mask providesprotection against NBC contamination byfiltering the air before it is inhaled.In general, all protective masks operate onthe same principles. As the wearer inhales, airis drawn into a filtering system. This systemconsists of a mechanical filter which clears theair of solid or liquid particles and a chemicalfilling (usually activated charcoal) which absorbsor neutralizes toxic and irritating vapors. Thepurified air then passes to the region of themask, where it can be inhaled. Exhaled air isexpelled from the mask through an outlet valvewhich is so constructed that it opens only topermit exhaled air to escape.Protective masks do not afford protectionagainst ammonia or carbon monoxide, nor arethey effective in confined spaces where theoxygen content of the atmosphere is too low(less than about 16 percent) to sustain life.When it is necessary to enter spaces wherethere is a deficiency of oxygen, the Navy oxygenbreathing apparatus (OBA) is used.DETECTION OF NBC CONTAMINATIONThe very nature of NBC contamination makesdetection and identification difficult. Nuclearradiation cannot be seen, heard, felt, or otherwiseperceived through the senses. Biologicalagents are small in size and have no characteristiccolor or odor to help in identification.Although- some chemical agents do have a characteristiccolor and odor, recently developednerve agents are usually colorless and odorless.It is obvious, then, that with contaminationwhich cannot be seen, smelled, felt, tasted, orheard, specialized methods of detection arerequired. Mechanical, chemical, and electronicdevices are available or under development forthe detection of NBC contamination.Detection of Nuclear RadiationThe instruments used for detecting radiologicalcontamination are known as radiacs ,the name being an abbreviation of radiation ,detection, indication, and computation . Varioustypes of radiacs are used aboard ship and atshore stations, since no single type of radiaccan make all the radiological measurementsthat may be required.The radiacs used aboard ship include (1)intensity meters for measuring gamma radiation;(2) intensity meters for measuring betaand gamma radiation; (3) survey meters formeasuring alpha radiation; and (4) dosimetersfor measuring accumulated doses of radiationreceived by individuals. These basic types ofradiacs are described briefly here. Specificinformation on operating principles and detailedinstructions for operating the instruments maybe obtained from the manufacturer's technicalmanual furnished with each instrument.GAMMA METERS. — Intensity meters formeasuring gamma radiation include both portableinstruments and fixed systems installedaboard ship. The intensity of gamma radiationis measured in roentgens per hour (r/hr) or inmilliroentgens per hour (mr/hr). The roentgenis a unit of measurement for expressing theamount of gamma radiation or X-ray radiation.A milliroentgen is 1/1000 of a roentgen. Radiacsused for measuring large amounts of gammaradiation are called high- range intensity meters ;these instruments are usually calibrated inroentgens per hour. Radiacs designed for measuringsmaller amounts of gamma radiation arecalled low- range intensity meters ; they areusually calibrated in milliroentgens per hour.Both high-range and low-range instruments arelikely to have several scales; a range selectorswitch allows selection of the appropriate scalefor each monitoring survey.BETA AND GAMMA METERS. -Intensitymeters which measure gamma radiation and alsodetect or measure beta radiation are usually ofthe Geiger-Mueller type. These instruments can75