What Are the Types of Fire?
Posted on 2nd October 2024
Understanding fire classes and flame types is crucial for ensuring safety in various environments. From everyday risks of combustible materials to the specialised needs of industrial settings, knowing how to identify fire scenarios is crucial.
This article explores the types of fire classes with causes, common setting and appropriate extinguishers. In addition, types of flames, alongside their colour and temperature levels.
Types of Fire Classes:
There are six types of fire classes in the UK, all with a different cause, common setting and appropriate extinguisher.
Class A: Combustible Materials
Cause: Class A fires are caused by naked flames or high-temperature items igniting combustible materials, such as paper and wood.
Common Settings: These fires often occur in offices, schools and hospitals.
Suitable Extinguishers: Water, foam, powder and wet chemical.
Class B: Flammable Liquids
Cause: Class B fires involve flammable liquids, such as petrol.
Common Settings: They are particularly dangerous in restaurants, garages and labs.
Suitable Extinguishers: Foam, powder and CO2.
Class C: Flammable Gases
Cause: Class C fires occur with flammable gases, such as propane and butane.
Common Settings: They often occur in industrial settings.
Suitable Extinguishers: Only powder extinguishers are appropriate.
Class D: Burning Metals
Cause: Class D fires involve combustible metals.
Common Settings: They are common in laboratories and fabrication settings.
Suitable Extinguishers: Only L2 powder extinguishers are appropriate.
*Class E: Electrical
Cause: Electricity of all types from any appliance or application.
Common Settings: Electrical fires can happen in any location.
Suitable Extinguishers: Powder (for currents under 1,000 volts) and CO2.
*Please note, the term “class E” is not commonly used. Instead, it is referred to as “electric fires.”
Class F: Cooking Oils and Fats
Cause: Class F fires are commonly caused by kitchen cooking oils and fats.
Common Settings: They are often found in kitchens (both commercial and residential).
Suitable Extinguishers: Water mist and wet chemicals.
Types of Fire Colours and Temperatures:
We commonly associate orange flames with fire, but you may recall blue flames from using Bunsen burners in school or from our oven hobs. Regardless of their colour, all flames can be hazardous. Understanding how different flames function and their levels of danger is essential for keeping people and buildings safe.
Green Flames:
Indicates: Results from the chemical composition of burned materials, such as copper compounds.
Temperature: Varies, generally similar to blue or orange flames.
Danger Level: Variable; depends on the materials burned.
Red Flames:
Indicates: Cooler temperatures, often in low-oxygen conditions or when burning inefficiently.
Temperature: Ranges from 600 to 800°C.
Danger Level: Moderate; often seen in smouldering fires.
Yellow/Orange Flames:
Indicates: Moderate temperatures with incomplete combustion, common in wood fires.
Temperature: Ranges from 1,100 to 1,200°C.
Danger Level: Moderate; hotter fire may spread easily, with increased smoke and gases.
White Flames:
Indicates: Very intense and efficient burn, typically with optimal fuel and oxygen mix.
Temperature: Ranges from 1,500 to 1,600°C.
Danger Level: High; represents a powerful energy release.
Blue Flames:
Indicates: A hotter, oxygen-rich burn, often seen in well-adjusted gas burners.
Temperature: Exceeds 1,600°C.
Danger Level: Low; signifies efficient combustion.
Types of Flames:
There are five common types of flames that you may find surprising. Each has its own cause, typical setting, colour, temperature and unique characteristics.
1. Natural Flames
Cause: Fueled by natural gas, coal or volcanic gases, often ignited by lightning or geothermal heat.
Common Settings: Natural sites, such as Eternal Flame Falls (USA), Door to Hell (Turkmenistan) and Yanar Dag (Azerbaijan).
Colour: Typically blue.
Temperature: Ranges from 300 to 600°C.
Characteristics: Continuous burning, spiritual significance in various cultures and can appear in diverse natural settings.
2. Turbulent Flames
Cause: Produced by combustion of hydrocarbon liquids or gases escaping from a pressurised source.
Common Settings: Furnaces, diesel engines, steam boilers, gas turbines and rocket motors.
Colour: Blue, yellow and red.
Temperature: Ranges from 300 to 1,000°C.
Characteristics: Rough and irregular appearance, faster propagation velocity, significant heat radiation and a structure made up of small laminar flames in a turbulent flow
3. Premixed Flames
Cause: Fuel and air are mixed before entering the burner.
Common Settings: Gas burners in kitchens and industrial applications.
Colour: Typically blue.
Temperature: Exceeds several thousand degrees; typically 2,121°C (air).
Characteristics: Stable combustion, fast ignition due to the complete mixture and a post-flame zone where the mixture relaxes to equilibrium.
4. Carburising Flames
Cause: Created in oxy-acetylene welding with excess acetylene.
Common Settings: Welding applications for metals, such as nickel and medium carbon steel.
Colour: Blue and white.
Temperature: Ranges from 3,100°C to 3,500°C.
Characteristics: Produces a gentle hiss and it chemically reacts with metal to form metal carbide.
5. Oxidising Flames
Cause: Excess oxygen in the combustion process, exceeding 100% stoichiometry.
Common Settings: Welding applications for metals, including copper, zinc and manganese steels.
Colour: Blue (becomes transparent).
Temperature: Typically 3,300°C, but can be higher.
Characteristics: Shorter appearance, distinct roar or hiss and oxidised metal surfaces.
Ensure Fire Safety with GRJ Contracting
Being informed about the different types of fire and the associated extinguishers is essential for maintaining safety in any setting. By recognising the unique properties of each fire class and the types of flames that can occur, individuals and businesses can take proactive measures to protect themselves and their properties.
GRJ Contracting specialises in passive fire protection, offering surveys, installation and remediation. With these methods, you can stop a fire before it gets too big or even begins! Contact us today for expert guidance and solutions tailored to your needs.
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