The minimum requirements for fire extinguishers on board aircraft operated under EU Ops are at least one hand fire extinguisher, containing Halon 1211, or equivalent as the extinguishing agent which must be conveniently located on the flight deck for use by the flight crew (Ops 1.790). Also, at least one hand fire extinguisher must be located in, or readily accessible for use in, the galley and at least one readily accessible hand fire extinguisher must be available for use in the baggage compartment if it is accessible to crew members in flight. Finally, for aircraft carrying 7-30 passengers at least one hand fire extinguisher must be conveniently located in the passenger compartment.
In reality, each extinguisher is placed within the aircraft to cover several locations. For example, on the 10 passenger Dassault Falcon 2000 there is an extinguisher in the cockpit behind the PIC, one at the forward end of the cabin near the galley and one at the rear end of the cabin near the entrance to the baggage bay. In the case of the Citation 550B there are just two fire extinguishers; one in the cockpit and just one at the aft end of the cabin as there is no access to the baggage bay in flight.
HALON extinguishers are used because the type and quantity of extinguishing agent within the aircraft must be suitable for the kinds of fires likely to occur in the compartment where the extinguisher is intended to be used. If this is in the passenger cabin it must also minimise the hazard of toxic gas concentration.
The aircraft manufacturers do not use one company to supply their extinguishers which is why there is such a variety of, albeit very similar style. In my company, we have extinguishers by AMEREX, Kidde and Pamel, but wherever they come from they all have much the same capability. The extinguisher gives approximately 8-10 seconds of fire fighting and has a range of 3 metres (10-12 feet).
The basic pre- flight checks of the extinguishers are also the same. Firstly, check is it there, is it sealed, and is it in its proper location. Next, check it is full (needle in the green zone), and that the safety pin is in place and has a plastic seal to keep it so.
Bear in mind there should only be one seal; some aircraft are delivered from the manufacturer with extra seals to stop the extinguisher discharging during delivery as shown below.
The HALON extinguisher does not produce a wide stream of gas like the CO2 extinguisher does. As can be seen from the following photo, the gas stream is quite compact and is easily directed on to the fire. However, it is quite forceful, so you do need to stand 2 metres (8-10 feet) away from the fire.