Unstable Burner Flame — B2B Guide

On a commercial or institutional gas burner, a stable blue flame is the sign of well-tuned combustion. As soon as it starts to flicker, pulse, lift off or turn yellow, it signals an imbalance in the air-to-gas mixture or a supply fault. Beyond the loss of efficiency, incomplete combustion can generate carbon monoxide, an odourless and toxic gas: an unstable flame is therefore as much a safety issue as a performance one.

What are the common causes of an unstable flame?

Several factors come up often: a poorly set air-to-gas ratio, insufficient combustion air or disrupted airflow (blocked air intake, negative pressure in the mechanical room), fouled injectors or a fouled burner head, gas pressure out of range, a partially blocked flue or unstable draft. Component wear and deposit build-up also play a part. Pinpointing the real cause takes measurement, not guesswork: an instrumented combustion analysis quantifies the CO level, excess air and actual efficiency.

What can be checked safely?

Without opening the burner enclosure or touching the gas train: observe the colour and stability of the flame through the dedicated sight port, note any code, indicator light or abnormal noise to relay to the technician, make sure the room’s combustion air intakes are not blocked, and confirm that the carbon monoxide detectors are working. If a detector sounds, occupants show symptoms or you smell gas, shut the unit down and evacuate. Any combustion adjustment is the job of qualified personnel.

When should you call a professional?

Call as soon as a flame stays unstable after these basic checks, when soot, deposits or a smell of incomplete combustion appear, or when a CO detector trips. Montréal Combustion serves Greater Montréal, the North Shore and the South Shore for B2B gas heating and combustion service: air-to-gas ratio measurement, combustion analysis, cleaning and re-tuning aligned with site requirements. 450-473-0909.

Frequently Asked Questions

Is an unstable flame dangerous?

It can be. A flame that flickers, lifts off or turns yellow can point to incomplete combustion, which produces carbon monoxide, an odourless and toxic gas. If a CO detector sounds, if occupants report headaches or nausea, or if you smell gas, evacuate and call qualified personnel without running the unit.

What causes an unstable flame?

Common leads include a poor air-to-gas ratio, insufficient or disrupted combustion air, a fouled burner or injectors, gas pressure out of range, a partially blocked flue or unstable draft. Only measurement can isolate the actual cause.

Can I adjust the burner myself?

No. Setting the air-to-gas ratio and working on the gas train are the job of a qualified technician, backed by an instrumented combustion analysis. A poor adjustment worsens the carbon monoxide risk. You can, however, note the symptoms and shut the unit down if in doubt.