Carbon monoxide is a colourless, odourless gas made by any incomplete burn, including a stove during start-up, with wet fuel or short of air, and its early symptoms of headache, nausea and drowsiness are exactly what a cold, tired person expects to feel anyway. If anyone feels sleepy or has a headache near a burning stove, put the fire out, open an inlet and an outlet, and get everyone into fresh air; do not lie down.
Part of Rocket Stove Design
Carbon monoxide forms when carbon burns without enough oxygen or heat to finish becoming carbon dioxide. It keeps coming from glowing embers after the flames are gone.
Why It Kills People Indoors
CO attaches to the haemoglobin in red blood cells far more strongly than oxygen does, so the blood carries less oxygen. The first signs are headache, nausea, dizziness and drowsiness, which a cold, tired person puts down to the cold and the hour. The drowsy person lies down, breathes more of it and does not wake. Symptoms can also appear days or weeks after a serious exposure.
The overview lists the signs: headache, dizziness, nausea, confusion. If anyone shows them while a stove is burning indoors, ventilate the space and move to fresh air immediately.
Sources In This Chapter
- A stove at start-up, with wet fuel, or starved of air.
- Glowing embers and charcoal.
- A sooting lamp or a multi-wick lamp in a closed room.
- A stove or duct that leaks into the room, or a draft that reverses.
How Little It Takes
Published exposure limits give a sense of scale. The WHO indoor air guidelines are 10 mg/m³ averaged over 8 hours, 35 mg/m³ over 1 hour and 100 mg/m³ over 15 minutes. The US NIOSH level considered immediately dangerous to life or health is 1,200 ppm. At room temperature 1 ppm of CO is about 1.15 mg/m³ (28.01 ÷ 24.45), so:
- 10 mg/m³ ≈ 8.7 ppm; 35 mg/m³ ≈ 30.6 ppm; 100 mg/m³ ≈ 87 ppm
- 1,200 ppm ≈ 1,375 mg/m³
Worked example. A closed room of 30 m³ (an illustrative size) with no air exchange:
- 10 mg/m³ × 30 m³ = 300 mg, so about 0.3 g of CO exceeds the 8-hour guideline.
- 1 g of CO: 1,000 mg ÷ 30 m³ ≈ 33 mg/m³ ≈ 29 ppm.
- The 1,200 ppm level: 1,375 mg/m³ × 30 m³ ≈ 41 g of CO.
No source is given here for how much CO a smouldering stove emits per hour, so none is claimed. The point is that the amounts are small, and a room with real air exchange dilutes them.
What To Do
- Prevent it. Burn dry fuel, keep the stove hot and clear, and exhaust it outside.
- Ventilate with an inlet and an outlet. A single cracked window is not enough.
- Never sleep with a stove, lamp or embers burning in a closed room.
- If symptoms appear: put the fire out if you can do so at once, open the inlet and the outlet, and go into fresh air. Rescuers should ventilate first.
- Keep resting in fresh air and watch the person for confusion, chest pain or fainting after the first symptoms ease. Get help for anyone who loses consciousness.
There is no flame test for CO: a flame burns normally at concentrations that kill a person. Do not use a candle or a match to judge the air.
Common Mistakes
- Putting the symptoms down to tiredness. That is how it kills.
- Trusting the lack of smoke. CO is invisible.
- Closing the damper on glowing embers. It traps CO.
Safety
No smell, no warning
Treat headache, nausea or drowsiness near a burning stove or lamp as carbon monoxide until proven otherwise. For the same hazard from charcoal burning, see CO Risk.
What’s Next
- Learn next: Indoor Use & Ventilation — prevention
- Combine with: Smoke Troubleshooting — stopping the cause