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（）.

Which action is routinely performed at the annual servicing and inspection of a dry-chemical cartridge-operated portable fire extinguisher?（）

When must a dry chemical fire extinguisher be recharged?（）

When should a fire be ventilated?（）

Which extinguishing agent is effective in combating an isoprene fire?（）

Which fire extinguishing agent can NOT be used on an ethylenediamine?（）

When water is used to fight a fire on board a ship，the effect of the weight of the water must be taken into account. How much sea water will increase the weight displacement by one ton?（）

When loading or discharging dry mud or cement，crew members should use facial respirator masks and（）.

Which characteristic of Halon is a disadvantage when it is used as a fire extinguishing medium?（）

Where would you find the FCC authorization for transmitting on your ship’s EPIRB?（）