Which option best describes the normal pilot flame characteristics?

Which option best describes the normal pilot flame characteristics?

• A. Mostly blue; envelops 3/8-1/2 inch
• B. Mostly yellow; envelops 1/4 inch
• C. Red; envelops 1 inch
• D. White; envelops 3/4 inch

Answer: (A)

A normal pilot flame should burn blue, indicating complete combustion with the proper air-gas mix. It should form a steady, tight flame that envelops the sensing element (like the thermocouple) by about 3/8 to 1/2 inch. This size is enough to reliably heat the sensor and keep the gas valve open without wasting gas or causing overheating. A mostly yellow flame points to incomplete combustion, often from insufficient air, dirty gas, or improper adjustment, which can lead to soot, CO buildup, and unreliable ignition. Flashes of red or white aren’t typical for a healthy pilot and suggest other issues. If the envelope is notably larger or smaller than roughly 3/8 to 1/2 inch, the pilot is out of adjustment and should be corrected.

A normal pilot flame should burn blue, indicating complete combustion with the proper air-gas mix. It should form a steady, tight flame that envelops the sensing element (like the thermocouple) by about 3/8 to 1/2 inch. This size is enough to reliably heat the sensor and keep the gas valve open without wasting gas or causing overheating. A mostly yellow flame points to incomplete combustion, often from insufficient air, dirty gas, or improper adjustment, which can lead to soot, CO buildup, and unreliable ignition. Flashes of red or white aren’t typical for a healthy pilot and suggest other issues. If the envelope is notably larger or smaller than roughly 3/8 to 1/2 inch, the pilot is out of adjustment and should be corrected.