in the scuba tanks as they are being charged. 4-7. OPERATION INSTRUCTIONS. 4-8. PRIOR  TO OPERATION  Prior to operating the service units, perform the following procedure. a. Transport the unit to work site and select as level an area as possible to park the Service Units.  Set hand brakes and stabilizing jack. High  pressure  gas  Is  dangerous  Check  all tubing     and     service     hoses     for     damage, cracks or deterioration b. Perform        all    inspection,        checks,    and services required Refer to Table 5-1 Under  no  circumstances  should   the   air   or oxygen purification cartridges in the purification   cylinders   (7,   8,   Figure   7-1)   be allowed to become contaminated with moisture If in doubt, change the cartridges Under  no  circumstances   will   cartridges   be interchanged    between    the    air    or    oxygen purified cylinders on a Type II system NOTE When air or oxygen  purification  cartridges  are  changed, make  certain  to  record  the  time  the  change  was  made Approximate time lapse for cartridge change is 8 hours Actual    frequency    of    cartridge    change    depends    on governing  weather  conditions  at  a  given  time  or  place, and the condition of the compressed gas (air or oxygen) being used c. Check    the    number     of     hours     that     the cartridges in the purifying cylinders have been used If the next period of operation will exceed the remaining useful life of the cartridges, replace the cartridges 4-9. TYPE I (AIR) - CHARGING THE TYPE I (AIR) SERVICING UNIT (See Figure 4-3 ) The  stems  and  seats  of  the  control  panel valves  may  be  damaged  by  overtightening All   valves   should   be   tightened   enough   to prevent leakage. a. Prior  to  attaching  the  service  hose  to  the servicing unit, make sure all valves are closed, including drain valves b. Attach a source of clean, dry, breathable air to recharge connection (9) on control panel. The  stems  and  seats  of  the  control  panel valves  may  be  damaged  by  overtightening All    valves  should  be  tightened  enough  to prevent leakage. c.   Close   manifold   shut-off   valves   (10),   open cylinder  valves  (2)  on  gas  cylinders  (1)  to  be  charged and  place  cam  lever  valve  (5)  m  the  up  position  Open recharge valve (8). d. Service air cylinder (1) to a maximum 3200 psi for breathable air (Type I). e. Close recharge valve (8) Do     NOT     disconnect     service     hose     until service    hose    line    has    been    bled    of    all pressure f. Open  service  hose  bleed  valve  located  on the source furnishing the breathable air. g. Disconnect service hose. h. Connect yoke adaptor (21) to scuba tanks i. Be sure scuba manifold bleed of valve (18) is closed j. Open manifold shut-off valve (10) k. Adjust regulator (12) to desired pressure I. Open  scuba  manifold  servicing  valve  (14) and scuba manifold charging valve (19) 4-5