NOTE: Remember you are dealing with high- -pressure gas. Before attempting to recharge any extinguisher, you should become thoroughly acquainted with the recharging pump and the methods of recharging. Carefully read the instruc- tions that pertain to the recharge pump and be sure all connections are tight at all times. C O₂ CYLINDERS AND SAFETY DISC Carbon dioxide cylinders should be charged with “bone-dry” carbon dioxide. Extreme care must be taken in the charging, weighing, sealing, and testing of cylinders. The safety discs of the cylinders are painted various colors to identify the pressure at which they will rupture. The correct color disc must be used in every case. All cylinders are manufactured in accordance with the requirements of the Interstate Commerce Commission (ICC) as set d o w n  b y  t h e  B u r e a u  o f  E x p l o s i v e s .  T h e s e requirements specify that the cylinder be tested to five-thirds of its normal working pressure and that the normal working pressure be stamped on the cylinder immediately following the letters ICC3A. We refer to this procedure as hydrostatic testing. Common cylinder stampings and the corresponding test pressures are as follows: Cylinder Test Color of Stamping Pressure Permissible Disc ICC 3 3000 psi White ICC 3A 1800 3000 psi White ICC 3A 2015 3360 psi White ICC 3A 2205 3680 psi White or red ICC 3A 2300 3840 psi White or red You should never use a disc in a valve where it would be working in connection with a different type of safety disc retainer. Never trim a safety disc to fit a valve other than the one for which it was intended. You will find similar markings on the shoulder of every cylinder. ICC 3A 1800 W. K. & Co. 221974 10-84 H An explanation of these marks follows: ICC 3A 1800 signifies the specific ICC test procedure followed. The number 1800 indicates the service pressure. 221974 is the cylinder serial number. Some cylinders have one or two letters as part of the serial number. (The U.S. Navy also assigns one of their numbers to all cylinders they purchase. This number has the letters USN accompanying it.) The letter H in a shield is the designation mark of the accredited ICC inspecting laboratory that supervises our tests. The letters W. K. & Co designate the manufac- turer of the cylinder. The numbers 10-84 mean that the cylinder was tested in October of 1984 and that its next test will be October 1989. Before any cylinder is recharged, the date must be checked; if more than 5 years has elapsed, the cylinder must be retested hydrostatically. The date of the retest is then stamped on the cylinder directly under the original date. This new date is the one against which future checks should be made. Remember you are dealing with high-pressure gas. Before recharging any cylinder, you must become thoroughly familiar with the proper procedure for recharging. When you handle or ship cylinders, the shipping cap should always be assembled on the cylinder. On cylinders where this is not possible, the cylinder should be carefully crated. Be thoroughly familiar with these procedures before you attempt to recharge any cylinder. A few minutes spent on becoming familiar with the procedure may prevent an accident involving injury to personnel or damage to equipment. WINTERIZING CARBON DIOXIDE CYLINDERS The PR is not normally tasked with the responsibility of recharging fire extinguishers and engine fire bottles. H o w e v e r ,  y o u  m a y  be assigned to an AIMD that supports aircraft that require winterizing of CO₂ cylinders. All carbon dioxide portable fire extinguishers installed in aircraft and all aircraft carbon dioxide built-in engine fire extinguishers are serviced to operate throughout the temperature range of –65°F to 160°F. The extinguishers are supercharged with the addition of 200 psi of dry, oil-free nitrogen. This servicing of extinguishers is done in connection with the U.S. Air Force winterization program. Extinguishers charged to meet this winterization requirement are identified by a yellow dot, three-fourths of an inch in diameter or larger, on opposite sides of the cylinder. Extinguishers so marked are winterized 3-11