After using a carbon dioxide fire extinguisher, the nozzle gets extremely cold.
What does this indicate?

Explanation:

A fire extinguisher, flame extinguisher or simply extinguisher is an active fire protection device used to extinguish or control small fires, often in an emergency situations.It is not intended for use on and out off control fire. Many types of fire extinguishers are available with different extinguishing 'agents' to deal with different classes of fires.

Many types of fire extinguishers are available with different extinguishing 'agents' to deal with different classes of fires. 

Water-filled extinguishers 

There are two methods of operation.

• Gas cartridge type
• Stored pressure type

Foam extinguishers:

These may be of stored pressure or gas cartridge types.

Foam extinguishers are most suitable for:

• flammable liquid fires
• running liquid fires

Must not be used where electrical equipment is involved.

Dry powder extinguishers:

• Extinguishers fitted with dry powder may be of the gas cartridge or stored pressure type.
• The main distinguishing feature is the fork-shaped nozzle.
• Powders have been developed to deal with class D fires. 

Carbon dioxide (CO2):

• This type is easily distinguished by the distinctively shaped discharge horn.
• Suitable for class B fires
• Best suited where contamination by deposits must be avoided.
• Not generally effective in the open air.
• If the nozzle gets extremely cold, then it is dangerous to use that Extinguisher.

Halon extinguishers:

• These extinguishers may be filled with carbon tetrachloride (CTC) and bromochlorodifluoro methene (BCF).
• They may be of either gas cartridge or stored pressure type.
• They are more effective in extinguishing small fires involving pouring liquids.
• These extinguishers are particularly suitable and safe to use on electrical equipment as the chemicals are electrically non-conductive.