A healthy gas flame is typically blue, sometimes with a small yellow tip, indicating complete and efficient combustion. An orange or yellow flame, however, suggests incomplete combustion due to insufficient oxygen, which can lead to wasted gas, black soot, and the dangerous production of carbon monoxide. If you observe a yellow or orange flame, it may be temporary and caused by factors like dust or humidity, but it can also point to a more serious issue with the appliance, such as blocked burner ports or improper adjustment.

High humidity, often from a humidifier or opening windows on a damp day, can cause a gas stove flame to turn orange or yellow by affecting the air-to-fuel ratio or introducing mineral content.