A.fixed foam systems to be ineffectiveB.faster cooling ……

单项选择题Before using a fixed CO2 system to fight an engine room fire，you must（）.

A.secure the engine room ventilation
B.secure the machinery in the engine room
C.evacuate all engine room personnel
D.All of the above

单项选择题Before a tank is to be crude oil washed，the oxygen content in the tank must be measured at a position（）.

A.immediately above the level of the oil
B.at the top of the tank
C.in the vent riser
D.one meter from the deck

单项选择题Backfire flame arrestors are installed on（）.

A.fuel tanks
B.spark plugs
C.carburetors
D.distributors

单项选择题Automatic fire dampers in ventilation systems are operated by use of（）.

A.remotely operated valves
B.fusible links
C.C0₂ system pressure switches
D.heat or smoke detectors

单项选择题Automatic fire dampers in ventilation systems are operated by a（）.

A.remote operated valve
B.fusible link
C.CO₂ system pressure switch
D.heat or smoke detector