A rocket stove that smokes persistently has one of five causes: wet fuel, blocked airflow beneath the fuel, too little insulation around the riser, too much fuel in the magazine, or a cold start. Dry the sticks first, clear the air path, add insulation, remove sticks and pre-warm the riser. Smoke is unburned fuel and carbon monoxide, so do not keep cooking in it.
Part of Rocket Stove Design
Smoke from a rocket stove is a symptom, and each cause has its own remedy.
Match The Symptom To The Cause
| Symptom | Likely cause | Fix |
|---|---|---|
| White steam, hissing sticks, then grey smoke | Wet fuel | Dry the sticks; store them under cover |
| Smoke and weak flame, sticks lying flat on the floor | Blocked air under the fuel | Make sure the shelf lets air pass beneath |
| Smoke and flame lazy even with dry fuel | Not enough insulation | Add insulation around the riser |
| Smoke and a choked, dull fire | Too much fuel | Remove some sticks |
| Smoke only in the first minutes | Cold start | Burn paper or tinder inside the riser first |
| Smoke out of the feed opening | Draft reversed or blocked | Stop; ventilate; clear the path |
Why Wet Wood Is Such A Problem
Boiling off water takes heat. The latent heat of vaporisation of water is about 2,257 kJ/kg (a standard value). Heating one litre of water from 20 to 100 °C takes about 4.186 × 80 ≈ 335 kJ. So each kilogram of water in the wood absorbs 2,257 ÷ 335 ≈ 6.7 times the heat needed to bring a litre of cooking water to the boil. That heat is taken from the chamber, which then runs cooler, and a cooler chamber smokes.
Common Mistakes
- Opening the stove to look. It breaks the airflow.
- Adding more fuel to cure smoke. Overloading is one cause.
- Cooking on in the smoke. Fix it first.
Safety
Smoke in the room is a carbon monoxide warning
If smoke comes out of the feed opening or leaks into a room, carbon monoxide comes with it, and you cannot smell that. Get everyone outside into fresh air, ventilate with an inlet and an outlet, and let the stove burn out before you return. Do not test the air with a flame. See Carbon Monoxide Risks.
What’s Next
- Learn next: Performance & Safety — measuring and staying safe
- Combine with: Ideal Fuel Sizes — dry, thin fuel