Classification of fires

Fires are classified in accordance with British Standard EN 2 1992 Classification of Fires. However for aii practical purposes there are FIVE main classes of fire -A, B, C, D and F, plus fires involving electrial equipment. BS 7937 2000 The Specification of Portable Fire Extinguishers for Use on Cooking Oil Fires introduced the new class F. The categories based on fuel and the means of extinguishing are as follows  

Class A - fires which involve solid materials such as wood, paper, cardboard, textiles, furniture and plastics where there are normally glowing embers during combustion. Such fires are extinguished by cooling which is achieved using water. 

Class B - fires which involve liquids or liquefied solids such as paints, oils or fats. These can be further subdivided into  

Class C - fires which involve gases such as natural gas or liquefied gases such as butane or propane. They can be extinguished using foam or dry powder in conjunction with water to cool any containers involved or nearby. 

Class D - fires which involve metals such as aluminium or magnesium. Special dry powder extinguishers are required to extinguish these fires, which may contain powdered graphite or talc. 

Fires are classified in terms of their types. BSEN 2 identifies five classifications. The classifications assist in recognising not only the type of fire but also the type of extinguishing medium that will need to be utilised to extinguish or suppress the fire. 

Class A - fires that involve solid materials, usually of an organic nature, such as wood, cardboard, paper, hardboard, soft furnishings such as carpets and curtains, in which combustion normally takes places with the formation of glowing embers. 

Class B - fires that involve liquids such as petrol, paraffin, white spirit, thinners, varnish and paints or liquefiable solids such as candles (wax) and fats. 

Class C - fires that involve gases such as LPG (i.e. butane, propane) or those involving natural gas. 

Class D - fires that involve metals such as sodium, lithium, manganese and aluminium when in the form of swarf or powder. 

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Fire-Resistant Hydraulic Fluids. The four classifications of fire-resistant hydrauHc fluids are Hsted below (7). Three of the four groups are fire resistant because they contain a significant amount of water which provides cooling and blanketing of the combustible materials. 

The tubes that are around the flame get most of their heat energs t rom radiation. The tubes in the top of the chamber get their heat from com ec-tion as the hot exhaust gases rise up through the heater and heat ihc process fluid in the tubes. The principal classification of fired heaters relates to the orientation of the heating coil in the radiant section. The tube coils of vertical fired heaters are placed vertically along the walls of the combustion chamber. Firing also occurs vertically from the Hoor of the heater. All the tubes are subjected to radiant energy. 

The National Fire Protection Association recognizes four general classification of fires."... 

Table 52.7 CETOP classifications of fire-resistant hydraulic fluids...

Fires are classified based on the type of fuel involved. Fuels are typically placed into three classes ordinary combustibles (like wood and paper), flammable liquids, and combustible metals. For firefighting, a fourth fire class, electrical fires, is also considered. The four main classifications of fire are shown in Table B-1. 

Fire hazard is viewed from the standpoint of safety, to which in the United States, the Occupational Safety and Health Standard (OSH) is often used as the basis for classification of flammables versus a combustible material. Additionally, the U.S. Department of Transportation also has very specific definitions regarding classification of fire hazards based on safe transport of materials. For initial discussions we will adhere to the OSHA definitions, and later refer to distinctions in U.S. federal definitions which are legal standards. 

Carbon dioxide fire extinguishers are widely used in laboratory fire fighting because the C02 does not damage apparatus or cause electrical shorts. Furthermore, carbon dioxide is effective against a wide variety of fires and is not toxic. The National Fire Protection Association adopts the following classification of fires ... 

The binder of a mastic is an organic resin dissolved in an organic solvent. A desirable resin is one which is fire-resistant and decomposes by evolution of gases which are preferably inert and nontoxic, and of maximum heat resistance. Some classifications of fire-resistant resins are ... 

There are a large number of different methods used for bench-scale assessment of combustion toxicity, and the applicability of test data to lire hazard assessment is not always clear. Obviously, toxic potency data should not be used in isolation but should either be a part of a classification scheme or as part of the input to lire risk and lire safety engineering assessments. It is important that uncertainty or confidence limits should be used with toxic potency data, because they are often relatively large. Fire effluent toxic potency does not have a unique value but is a function of the material and the fire conditions, particularly temperature and oxygen availability in the fire zone, and also the fire environment (enclosure, geometry, and ventilation). To assess the fire hazard, toxic potency data must be relevant to the end use fire situation, and the fire condition, which can be defined using the ISO classification of fire stages. 

The following two test methods are suited to solid oxidizers according to the classification of Fire Service Law. 

Fire Classification - Classifications of fires developed by the National Fire Protection Association. 

The specific causes and agents contributing to fires differ, and the methods to fight these different fires vary. Because of this, the National Fire Protection Association (NFPA) has classified fires into foiu t3q>es. Fire extinguishers should be labeled with the classes of fires they extinguish. Use the following chart to see the classifications of fire and extinguishers. 

Table 7.2 Classification of fire ants characterized by gas chromatography data (from Brill etal. 1985, with permission of Elsevier Science)...

BS 5423 1987 Portable fire extinguishers, British Standards Institution, London Classification of Fire Hazards in Buildings, Fire Offices Committee, London (1973)... 

BS 3116 Automatic fire alarms in buildings Part 1 1970 Heat sensitive (point) detectors Part 4 1974 Control and indicating equipment BS 4422 Glossary of terms associated with fire Part 1 1969 The phenomenon of fire Part 2 1971 Building materials and structures Part 3 1972 Means of escape Part 4 1975 Fire protection equipment Part 5 1976 Miscellaneous terms BS 4547 1972 Classification of fires... 

Table 23.8 EC classification of fire tests for construction products... 

General Classification of Fire Retardants and Their Choice... 213... 

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