marked with an arrow to show direction of flow and uses the standard symbols shown in figure 5-9, and hazard marking, as you will see later in this chapter. that it includes a symbol list. Some small piping The  following  paragraphs  contain  markings  for  the diagrams do not include a symbol list; therefore, you four general classes of hazards, and figure 5-12 shows must  be  familiar  with  the  standard  symbols  to examples of the hazards in each class. interpret  these  diagrams. FLAM — This marking identifies all materials ordinarily known as flammable or combustible. TOXIC — This marking identifies materials that are extremely hazardous to life or health. AAHM — This marking identifies anesthetics and harmful materials. These include all materials that produce anesthetic vapors. They also include those that do not normally produce dangerous fumes or vapors, but are hazardous to life and property. PHDAN — This marking identifies a line that carries material that is not dangerous in itself, but is asphyxiating  in  confined  areas.  These  materials  are generally handled in a dangerous physical state of pressure  or  temperature. SHIPBOARD PIPING PRINTS There  are  various  types  of  shipboard  piping systems. Figure 5-13 shows a section of a piping diagram for a heavy cruiser. Note that the drawing Standard  symbols  are  generally  not  used  in drawings  of  shipboard  piping  systems  found  in operation  and  maintenance  manuals.  Each  fitting  in those systems may be drawn in detail (pictorially), as shown in figure 5-14, or a block diagram arrangement (fig. 5-15) may be used. HYDRAULIC PRINTS The Navy has increased its use of hydraulic sys- tems, tools, and machines in recent years. Hydraulic systems  are  used  on  aircraft  and  aboard  ship  to activate   weapons,   navigational   equipment,   and remote controls of numerous mechanical devices. Shore  stations  use  hydraulically  operated  main- tenance   and   repair   shop   equipment.   Hydraulic systems are also used in construction, automotive, and weight-handling    equipment.    Basic    hydraulic principles are discussed in the basic training course Fluid Power, NAVEDTRA 12064. To help you distinguish one hydraulic line from another, the draftsman designates each line according FLUID Air (under pressure) Alcohol Carbon  dioxide FREON Gaseous oxygen Liquid  nitrogen LPG (liquid petroleum gas) Nitrogen  gas Oils  and  greases JP-5 Trichloroethylene HAZARD PHDAN FLAM PHDAN PHDAN PHDAN PHDAN FLAM PHDAN FLAM FLAM AAHM Figure 5-12.—Hazards associated with various fluids. 5-8