Why does a pellet stove smoke (or fail to ignite)? 5 common causes and quick solutions

The 5 main causes explained (and how to fix them)

Correct diagnosis is essential. Smoke is always a symptom of incomplete combustion. Let’s see why this happens.

1. Blocked or dirty flue (the number one enemy)

This is the most common and dangerous cause of smoke re-entering the room.

• The problem: accumulated soot narrows the passage, or worse, bird nests may completely block the exhaust. If fumes cannot exit, they flow back into the stove.
• The solution: professional flue cleaning by a certified chimney technician is mandatory, at least once a year before the heating season, as required by regulations.

2. Dirty or clogged burn pot

If the stove “chokes” during ignition or produces thick smoke, the issue is often at the heart of combustion: the burn pot.

• The problem: as pellets burn, they leave residues (clinker). If the burn pot is not cleaned daily, its holes become clogged. Combustion air cannot flow properly, the flame is weak, and pellets accumulate, producing smoke instead of a lively flame.
• The solution: perform daily cleaning of the burn pot using an ash vacuum. Make sure all holes are clear before every ignition.

3. Poor-quality or damp pellets

The stove is designed to burn optimal fuel. Unsuitable pellets only cause problems.

• The problem: pellets with high moisture content (above 8–10%) or rich in resins and binders swell during combustion, burn poorly, and produce excessive smoke and ash, quickly blackening the glass.
• The solution: use only ENplus A1 certified pellets. Store the bags in a dry place, away from damp walls or floors.

4. Electrical issues: the glow plug doesn’t heat up

If the stove loads pellets, attempts to start but does not produce a flame (and after a while goes into “failed ignition” alarm), the issue is almost certainly electrical.

• The problem: the glow plug is the electrical heating element that becomes incandescent to ignite the first flame. Over time, it wears out and fails. If it’s broken, pellets will accumulate in the burn pot but never ignite.
• The solution: this is a technical intervention. The glow plug must be replaced by an authorized service center.

5. Worn gaskets and draft problems

If the stove smokes and the glass turns black very quickly, there may be an air intake issue.

• The problem: the gaskets (the braided rope seals) around the firebox door and ash drawer must ensure airtight sealing. If they are worn, the stove draws “false” air from the wrong points. This disrupts the balance between air and fuel, worsening combustion and causing smoke.
• The solution: check the condition of the gaskets. If they appear dry, frayed, or flattened, they must be replaced.

Maintenance: prevention is the best solution

To avoid smoke and ignition failures, prevention is key. A proper maintenance plan ensures efficiency and safety:

• Daily cleaning: empty and clean the burn pot.
• Weekly cleaning: vacuum the ash drawer and combustion chamber.
• Annual service (technician): full stove cleaning, component checks (gear motor, gaskets, glow plug), and certified flue cleaning.