單項(xiàng)選擇題

When using a high-velocity fog stream in a passageway，the possibility of a blow back must be guarded against. Blow back is most likely to occur when（）.

A.pressure builds up in the nozzle which causes a surge of water
B.the only opening in a passageway is the one from which the nozzle is being advanced
C.pressure in the fire hose drops below 100 psi
D.a bulkhead collapses due to heat and pressure

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單項(xiàng)選擇題

When used to fight fire，carbon dioxide（）.

A.is effective if used promptly on an oil fire
B.has a greater cooling effect than water
C.is lighter than air
D.is harmless to cargo and crew

單項(xiàng)選擇題

When two fire hose teams are attacking a fire they should（）.

A.use different fire hose pressures
B.use fire hoses of different sizes
C.not attack the fire from opposite sides
D.not wear protective clothing

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When using a high-velocity fog stream in a passageway，the possibility of a blow back must be guarded against. Blow back is most likely to occur when（）.

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When used to fight fire，carbon dioxide（）.

When two fire hose teams are attacking a fire they should（）.

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When using a high-velocity fog stream in a passageway，the possibility of a blow back must be guarded against. Blow back is most likely to occur when（）.