What is the Temperature of Fire?
Fire is versatile and dangerous. No matter what kind of industry you belong to, a working knowledge of the properties of fire is an important part of fire safety. The temperature of fire varies depending on the source and kind of fire you’re dealing with.
Understanding the nuances of fire temperature will inform your overall knowledge of fire and how it works, so in this article we’re looking at the temperature of fire and how you can identify it.
Temperature and colour
The two most distinguishing properties of fire are heat and colour. The colour of a flame is directly influenced by the temperature, so you should be able to estimate the temperature of a fire by identifying the colour of the flames.
Fire is a result of combustion – a chemical reaction between a fuel and oxygen – and when the reaction produces enough heat, flames are formed. Flames themselves change colour over time, and will usually have multiple colours in different parts of the flame.
The hottest part of the flame is the base, so this typically burns with a different colour to the outer edges or the rest of the flame body. Blue flames are the hottest, followed by white. After that, yellow, orange and red are the common colours you’ll see in most fires.
It’s interesting to note that, despite the common use of blue as a cold colour, and red as a hot colour – as they are on taps, for instance – it’s the opposite for fire. Red is usually seen on the outer edge of the flame, where the temperature is lower, while blue is the fiercest, hottest temperature.
Of course, just because there is a hierarchy of temperature for fire, that doesn’t mean that red flames are in any way cold. The fact that you can see flames at all means that the combustion rate is high, so the fuel is burning at a very high temperature.
While weaker, red flames can still range from 525°C to 1000°C. The more faint the colour, the lower the temperature. A more vibrant red, something closer to orange, will hit the higher end of the scale measuring nearer the 1,000°C mark.
Orange flames range from around 1100°C to 1200°C. White flames are hotter, measuring 1300°C to about 1500°C. The brighter the white, the higher the temperature.
For blue flames, or flames with a blue base, you can expect the temperature to rise dramatically, hitting roughly 2500°C to 3000°C. A bunsen burner or oven hob are the most obvious examples of blue flames. As you might expect, gas burning fires reach higher temperatures than materials such as wood, paper or textiles, so businesses which store gas tanks such as propane, for example, are most likely to see fires that reach the highest possible temperatures.
Candle flame – The hottest part of a candle flame burns at around 1400°C, while the average temperature is usually 1000°C.
Wood fire – A household wood fire burns at around 600°C. Temperature can change depending on the type of wood and its condition.
Bonfire – The temperature of a bonfire gradually heats up to around 600°C, but bonfires can reach 1000-1100°C.
Bunsen burner – A bunsen burner is adjustable, with safety flames measuring around 300°C. Fully open bunsen burners can reach 1500°C, with piercing blue and white flames visible.
Burning match – For such a small flame, a household match burns at around 600-800°C.
Propane torch – Combustion of propane and air is roughly 1900°C. A butane fire will have a similar temperature.
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