S 912-412

 (4)  
The fuel tank must be in a health-safe condition before you can go into the fuel tank without a breathing-air supply. When the fuel tank is in a health-safe condition, at a minimum, it is recommended that a half-mask respirator with an organic vapor filter be used. It is necessary to have a good flow of air through the fuel tank to get a health-safe condition. The air must flow continuously during the fuel tank entry procedure.

 S 912-413

 (5)  
Hydrocarbon fuels that touch the skin can remove protective oils. Without protective oils, the skin can become dry, chapped, cracked, or possibly become infected. If a person breathes too much fuel vapor, the person can become dizzy, get a headache or lose his or her coordination. Jet fuel is composed of many different kinds of hydrocarbon molecules. Exposure to some of these molecules for a long time is known to cause cancer.

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747-400 MAINTENANCE MANUAL
 S 912-414
 (6)  
Vapors from fuel or other materials (solvents etc.) used for fuel tank maintenance can replace oxygen from a confined area such as a fuel tank or dry bay. If a person goes into a confined area that contains fuel vapor (or other vapors) without an air supply, the person may not get enough oxygen. This may cause unconsciousness or death. Make sure the environment is continously monitored with an approved combustible gas indicator.

 S 912-415

 (7)  
No one is allowed to go into or remain in a fuel tank if:

 (a)  
The flammable vapor concentration is more than 10% of the lower explosive limit.

 (b)  
The oxygen content of the fuel tank is below 19.5% or above 23.5%

 (c)  
The air ventilation system fails.

 (d)  
A strong fuel odor is noticed.

 (e)  
A person feels any physical problems, such as trouble breathing, dizziness, irritation, confusion, light-headedness, fullness in the head, ringing sensation on the ears, nausea, headache, difficulty in breathing, sensation of apparent suffocation, immobility, unusual behavior, failure to respond to communication, or other signs of illness.

 (f)  
There is an observed or reported hazard which may reduce the level of safety.

 S 912-416
 (8) Persons who work in or near an open fuel tank must not:___
 (a)  
Slide metal objects, such as tool boxes, ladders, etc.

 (b)  
Carry matches or pocket warmers

 (c)  
Wear shoes with metal clips or exposed nails

 (d)  
wear or use battery-operated devices such as hearing aids, electrical pacemakers or watches, pocket radios, cellular phones or paging equipment unless it is explosion-proof and permitted by approved persons.

 S 912-417
 (9)  
Persons who work in an open fuel tank must wear approved fuel tank protective clothing. Protective clothing includes:

 (a)  
Cotton coveralls with non-sparking zippers or buttons. Do not wear wool, silk, nylon or other synthetic clothing.

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747-400
MAINTENANCE MANUAL

 WARNING:_______ COVERALLS THAT ARE COATED WITH SARANEX 23P WILL KEEP BODY
 HEAT IN.  MAKE SURE THE TEMPERATURE IN THE FUEL TANK DOES
 NOT GET TOO HOT.  IF THE FUEL TANK TEMPERATURE GETS TOO
 HOT, A PERSON IN SARANEX 23P COVERALLS CAN HAVE
 HEAT-RELATED DISORDERS.  IF A PERSON BECOMES TOO HOT, GET
 THE PERSON OUT OF THE FUEL TANK.  FIND OUT IF MEDICAL

 ASSISTANCE IS NECESSARY.
 (b)  
Saranex coveralls are also approved for use in fuel tanks.

 (c)  
Clean cotton boot socks or fuel cell boots.

 NOTE: It is recommended that boot socks be worn over fuel cell
____ boots when you stand in a fuel tank. This will reduce the chance that you will slip and fall down.
　
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