Why is my flame yellow instead of blue?

Flame colour is a diagnostic. Blue is the gas burning fully; yellow is gas burning badly.

What makes a flame blue?

Complete combustion. When the burner draws the right amount of air into the gas before it ignites, everything burns and the flame is blue and steady with a defined inner cone.

What makes it yellow?

Not enough air reaching the gas. The most common causes are:

• Clogged burner ports — spilled food, grease and dust blocking the small holes.
• A blocked air intake on the burner body.
• A dirty or misaligned burner cap sitting unevenly.
• Pot too close to the burner, disturbing the air draw.

Why does it matter?

Two reasons, and both cost money.

Unburnt gas leaves through the flame, so you are paying for fuel that does no cooking. And incomplete combustion deposits soot, which is the black film that builds up on the base of your pots.

Soot on a pot base also insulates it, so the next meal takes longer and uses more gas again.

How do you fix it?

1. Turn off the gas at the regulator and let the burner cool completely.
2. Lift off the burner cap and head.
3. Clear each port with a pin or a stiff brush — not a matchstick, which can break off inside.
4. Wash the parts, dry them fully, and refit the cap so it sits flat and square.
5. Relight and check the flame.

If the flame is still yellow after a proper clean, the burner or the regulator may need attention from a qualified gas fitter.

Can the gas itself cause a yellow flame?

Blend and moisture content do affect how cleanly gas burns. A correct propane and butane mix with low sulphur and low moisture burns blue and steady and leaves less deposit.

But before assuming the gas, clean the burner. That is the cause the great majority of the time.