Flame temperatures

Last updated April 6, 2005.

Flame temperature is not as simple as it sounds. It depends on many factors, such as:

• Whether the (gaseous) fuel flow is laminar (smooth) or turbulent
• Whether the fuel and oxidixer are premixed, or simply diffuse together while burning
• Whether the flame is "adiabatic", meaning that it does not lose heat. While impossible in practice, the theoretical adiabatic temperature is often quoted.
• Where in a (laminar) flame the temperature is measured
• For flames in air, the temperature, humidity, pressure, present gas mixture, etc. of the air
• The mixture of fuel vs. oxidixer in use. For example, an acetylene/oxygene flame may be neutral (equal mix: complete combustion, white rounded cone); carburising (excess acetylene: large smoky yellow flame); or oxidising (excess oxygen: short, sharp inner cone, deeper purple hissing flame).

Sites discussing practical welding and similar tasks tend to give much lower numbers than science-oriented sites, probably because of rapid heat loss in typical use. A number of sites warn that measurements done with thermocouples can be wildly inaccurate. More definitive information is available in the North American Combustion Handbook.

As a general practical guideline, consider one site's list of these heats for their jewelers' (gas/oxygen) torch:

• 2200°C = 3992°F, for Propane/Oxygen
• 2927°C = 5300°F, for MAPP Gas/Oxygen
• 2700°C = 4892°F, for Acetylene/Oxygen
• 3200°C = 5792°F, for Hydrogen/Oxygen

For their fuel/air torch they list:

• 1225°C = 2237°F with Propane-Butane Gas

For more theoretical/ideal values, consider this table (which also includes a few temperatures other than for gas/oxidixer mixtures):

Fuel and Oxidizer type	Temperature (Celsius)
Fluorescent light	60-80
Incandescent light	100-300
Cigarettes - unventilated conditions	288
Cigarettes - ventilated	400-780
Cigarettes - insulated and smoldering	510-621
Stove element	>550
Match	600-800
Tungsten halogen light	600-900
Candle flame	600-1,400
Electrical spark	1,316
Bunsen burner	1,570
Methanol/air	1,910
Methane/air	1,920-1,949
Butane/air	1,977
Propane/air	1,977
Wood/air (most organics are about here))	~1977
MAPP Gas/air
Hydrogen/air	2,210
Carbon monoxide/air	2,468
Acetylene/air	2,632
Acetylene/Oxygen	3,300
Hydrogen/Oxygen
Electrical arcing	<3,750
Plasma torch	~4,700
Lightning	30,000