There is no picture symbol for Class D extinguishers. All fire extinguisher nameplates have either the letter or picture symbols described above. The newer picture symbols use the International sign system diagonal red slash to indicate a potential hazard if the extinguisher is used on that particular type of fire. Absence of a picture symbol means only that the unit is not recommended as particularly effective for that class, but not dangerous if used in error. It is important to be familiar with the basic design of portable fire extinguishers.
Most extinguishers consist of the basic parts described below.
The body of a typical stored pressure extinguisher is constructed of either low carbon steel or aluminum. The cylinder holds some combination of extinguishing agent and expellant gas. A large nameplate affixed to the cylinder contains information about operating instructions, the extinguishing agent and the class of fires against which the extinguisher is effective. Pressure gauge The operating range of an extinguisher and its ability to expel all of its extinguishing agent decrease as the pressure drops. The pressurized water and multi-purpose dry chemical and sodium chloride dry powder extinguishers all have pressure gauges.