What is the temperature of a neutral flame?

• A. 5600 degrees F
• B. 3000 degrees F
• C. 1200 degrees F
• D. 8000 degrees F

Answer: (A)

The key idea here is the heat output of a neutral flame produced by a perfectly balanced fuel-to-oxidizer mix. When the flame is neutral, the acetylene and oxygen combine in a stoichiometric ratio, yielding a clean, fully combusted burn with no excess fuel or oxygen. That balance creates a very hot flame, typically cited around 5600 degrees Fahrenheit, which is hot enough to melt metal for welding while staying stable and clean. The number around 5600 F is a standard reference value used in welding training to represent a neutral flame’s temperature.

Other options are not representative of a neutral flame’s temperature. A much cooler value like 3000 F wouldn’t provide the intense heat needed for welding, and 1200 F is far too low. An 8000 F figure would be outside the common range for typical acetylene-oxygen setup and isn’t used to describe a neutral flame in standard practice.