Fire extinguishing system

Purpose of the fire protection system:  to deliver fire protection agents (water, foam, inert gases, vapours, and easily evaporating liquids.) to the fire site and to ensure preventive actions to control the spread of fire (interruption of air, supply of combustible materials to the fire place, isolation of the fire room, etc.).
Ships shall be equipped with the following fire protection systems: water (watering, fencing, spraying), foam extinguishing, inert gas fighting, carbon dioxide fighting, steam fighting, liquid/chemical extinguishing.
Fire is possible only if three factors are affected at the same time, that is, a high temperature is heated to a combustible material in contact with enough oxygen. However, in the event of a fire, its spread must be stopped by reducing: the heat permeability of the ship's metal structures and bulkheads; radiant and concentrated heat metabolism.
The main causes of fires on board ships are:

• faults in electrical circuits and equipment and discharge of atmospheric, static electricity;
• Ignition of flammable liquids and vapours (e.g. fuel or oil on hot parts of machinery);
• Spontaneous combustion of materials and cargo due to non-compliance with the safety regulations for cargo transportation;
• Violation of repair regulations, careless smoking;
• Arson.

Fires are divided into four classes marked with the letters „A“to „D“:

     A.  Fires from simple combustible materials such as wood, fabric, paper, rubber, and many plastics.
B.  Fires from flammable liquids, oils, greases, tars, oil paints, varnishes and flammable gases.
C.  Fires related to voltage, electrical equipment;
D.  Fires in the presence of flammable metals such as magnesium, titanium, zirconium, sodium, lithium and potassium.

Class A fires shall be extinguished by means of accessible extinguishing agents, such as water from the main fire protection system.
Class B fires shall be extinguished by fixed fire protection systems for gases, water sprinklers or quick-spreading foams and portable fire protection systems for dry powders. In cargo tanks for flammable liquids, inert gas systems are used to maintain inert conditions in cargo tanks.
In the event of a Class C fire, any electrical installation shall be disconnected from the voltage. In the absence of disconnection of the electrical installation, the flame must be extinguished using an electrically impermeable material, such as CO₂ or a dry chemical.
NOTE: Electrical equipment bordering or its presence in the vicinity of a fire can cause electric shock and burns.
The Class D fire extinguishing method is not effective. Sand, graphite, various other powder extinguishing agents and salts, various types of them were applied to the firefighting of metals with variable success. Therefore, recognizing the unique fire risk presented by individual hazardous metal cargoes, the International Maritime Organization (ICC) has made a few significant improvements to the risk of fire. The International Maritime Organization has developed emergency procedures for such products. The purpose of this emergency procedure is to determine the type of metal extinguishing agent to be used in the event of fire.