Halon extinguishers used on a class C fire should be directed at the（）.

A . mechanical foam B . chemical foam C . carbon dioxide D . soda acid

A . alternate expansion and contraction as water in a liquid state becomes a vapor B . absorption of smoke and gases as water is converted from a liquid to a vapor C . rapid contraction as water is converted from a liquid to a vapor D . rapid expansion as water absorbs heat and changes to steam

A . outside B . on class C fires C . in an emergency D . on class B fire

A . solid materials such as wood or bales of fiber B . flammable liquids C . electrical equipment D . metallic solid

A . Fires in electrical equipment B . Flammable oils and greases C . Class A fires in ordinary combustibles D . Materials containing their own oxyge

A . breaking the chain reaction B . smothering the fire C . cooling the fire D . coating the fuel with a nonflammable surface

A . put back in service if some CO remains B . hydrostatically tested C . retagged D . recharged

A . used for electrical fires only B . the smallest C . the most accessible D . the most effective

A . dry chemical or foam B . foam or soda acid C . carbon dioxide or foam D . carbon dioxide or dry chemical

A . displacement of oxygen B . skin irritation C . inhaling toxic vapors D . eye irritatio

A . Electrically non-conductive B . Relatively inexpensive C . Effective against chemicals containing an oxidizer D . All of the above

A . urgency B . emergency C . immediacy D . crisi

A . Conducts electricity B . Difficult to store C . Large volume necessary to be effective D . Ineffective in powdered metal fire

A . soild materials such as wood or bales of fiber B . flammable liquids C . a piece of electrical equipment D . combustible metallic solid

A . water B . foam C . the range hood extinguishing system D . fire damper

A . put back in service if some C0 remains B . hydrostatically tested C . retagged D . recharged

A . generators B . oil drums C . the bridge controls D . combustible metal

A . cooling B . smothering C . shielding of radiant heat D . breaking the chain reactio

A . put back in service if some CO remains B . hydrostatically tested C . retagged D . recharged

A . at the top of the flames B . at the base of the fire near the edge C . in short quick bursts D . toward the upwind side of the fire

A、 salt water B、 foam C、 low velocity fog D、 co2

A.CO2 B.ABC dry chemical C.CO2 propelled foam D.All of the above