S 492-463
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747-400 MAINTENANCE MANUAL
 S 942-464
 (11)
 Continue to have a good flow of air through the fuel tank with the air mover until you prepare to the close the fuel tank.

 (a)  
Read the combustible gas indicator values every half hour or less.

 S 942-465
 (12)
 If fuel vapors get into the fuel tank that was in a fire-safe condition, get all persons out of the fuel tank until you make sure the air in the fuel tank is in a fire-safe condition again.

 S 942-466

 (13)
 Go into the fuel tank per the "Fuel Tank Entry" procedure to do maintenance.

 L.
Fuel Tank Entry

 S 912-467
 WARNING:_______OBEY THE PURGING AND FUEL TANK ENTRY PRECAUTIONS. FAILURE TO OBEY THE PURGING AND FUEL TANK ENTRY PRECAUTIONS CAN CAUSE SERIOUS INJURY OR DEATH TO PERSONS AND DAMAGE TO EQUIPMENT.
 (1)  
Read and obey the precautions in this task: Purging and Fuel Tank Entry Precautions.

 S 972-468

 (2)
Complete the confined space entry permit (if it a requirement).

 S 972-469

 (3)
Use the pre-entry checklist (an example is given in Figure 206).

 S 492-470

 (4)
Do these steps to prepare the respirators for fuel tank entry:

 (a)  
Use Table 203 to find out what level of respiratory protection is necessary.

 (b)  
If the fuel tank is in a fire-safe condition, wear a full-face respirator with an attached breathing-air supply.

 WARNING: PUT ON AN APPROVED RESPIRATOR WITH ATTACHED BREATHING-AIR
_______ SUPPLY BEFORE YOU GO INTO A FUEL TANK THAT WAS FILLED WITH JP-4/JET-B FUEL. THERE IS NO HEALTH-SAFE LIMIT FOR JP-4 /JET-B WHICH CAN CONTAIN BENZENE. IT IS POSSIBLE THAT BENZENE CAUSES CANCER.
 (c)  If the fuel tank contained JP-4 or Jet B, wear a full-face respirator with an attached breathing-air supply.
 NOTE: There is not a health-safe limit for JP-4 or Jet B.
____
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747-400 MAINTENANCE MANUAL
 (d)  
If the fuel tank is in a health-safe condition, wear a full face respirator with an attached breathing-air supply, or at a minimum, a half-face respirator with an organic vapor filter.

 (e)  
Connect the subsequent respirators to the air supply (Fig. 204): 1) One respirator for the person who goes into the fuel tank. 2) Two emergency rescue respirators.

 (f)  
Make sure air gets to the respirators.

 (g)  
Make sure the respirator system (regulator, mask etc.) is clean.

 NOTE: When you use the respirator, you should regularly drain
____ moisture from the filter on the regulator. If you drain dirt or oil from the filter, or if the air in the respirator smells bad, replace the filter.
 (h)  Make sure the emergency air supply and respirators operate correctly.
 ~..............................................................................
 |  |
 |  FIRE-SAFE CONDITION  |
 |  |
 |  A FIRE-SAFE CONDITION OCCURS WHEN THE VAPOR CONCENTRATION IS  |
 |  LESS THAN 10% OF THE LEL.  |
 |  |

 2..............................................................................1

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