This page is the medical half
The prevention, the ventilation rules, the alarm standard and the list of what must never be burned indoors are all on carbon monoxide and ventilation in the fire domain. That page is the one to read before running any burning appliance, and it is not repeated here.
This page covers recognising poisoning in a person and what to do about it.
It matters disproportionately in this app's scenario, because every alternative to mains heating and cooking produces carbon monoxide, and because the people most at risk are the ones sleeping in the one heated room next to the only fire in the house.
The pattern that identifies it
You cannot detect the gas. You can recognise the pattern, and there is one that is genuinely distinctive.
Look for it across the household, not in one person. If several people, or the people and the pets, all feel unwell at once with headaches and tiredness and nobody has a temperature, that is carbon monoxide until proven otherwise.
Symptoms by blood saturation, which is the measure clinicians use:
| Carboxyhaemoglobin | Effect |
|---|---|
| 10 to 20% | Headache, nausea |
| Over 20 to 30% | Dizziness, weakness, poor concentration, impaired judgement |
| Over 30% | Breathlessness on exertion, chest pain, confusion |
| Over 60% | Collapse, coma, respiratory failure, death |
Long, low-level exposure over weeks gives something different again: persistent tiredness, headaches, poor memory and concentration, disturbed sleep, low mood, and vague unexplained symptoms. It is routinely mistaken for stress, depression, or a virus that will not shift, and in a cold house with a poorly ventilated stove it can go on all winter.
Other signs worth knowing: the traditional teaching of cherry-red skin is unreliable and usually a late or post-mortem finding, so its absence proves nothing. Symptoms that are worse in one room, or worse in the mornings, point at a source.
What to do
Why oxygen matters and time does not help much
Carbon monoxide binds to haemoglobin roughly 200 times more readily than oxygen does, and it does not let go quickly.
On ordinary air, it takes around 4 to 6 hours to shed half of it. That is why:
- Getting out of the room is a first step, not a cure. Someone in fresh air is no longer accumulating it, and is still carrying most of what they already have.
- They can deteriorate after leaving. Feeling better outdoors does not mean the blood has cleared.
- High-flow oxygen is the treatment, and it cuts that clearance time dramatically. That is what the ambulance brings and it is the main reason to call.
- Severe cases may need hyperbaric oxygen, which is a hospital decision.
With no medical help reachable at all, the honest position: fresh air, rest, no exertion, warmth, fluids, and time. There is no home treatment that speeds clearance. Keep them under observation for at least 24 hours, and understand that they will be tired and headachy for some days.
Who is affected first
Not evenly distributed, and knowing the order tells you where to look for the first sign.
- Pets, particularly small ones. A poorly bird or a lethargic cat is a recognised early warning, and in the days before detectors, caged birds were used for exactly this.
- Babies and small children, who have a higher metabolic rate and smaller bodies.
- Anyone pregnant. CO crosses the placenta and the foetus is affected more severely than the mother, so a pregnant woman with any suspected exposure needs assessment regardless of how mild it seems.
- Older people, and anyone with heart or lung disease, in whom the reduced oxygen delivery matters sooner.
- Anyone exerting themselves, because they are breathing more.
In a household sleeping in one heated room, everyone is in the same exposure. That is the whole reason the pattern across people is the useful signal.
Afterwards
- Recovery is usually complete from a mild single exposure, and headaches and tiredness can persist for days.
- Delayed neurological effects are real. In a minority of significant exposures, problems with memory, concentration, mood or coordination appear days to weeks later, after apparent recovery. Anyone who was significantly exposed should be reviewed, and this is worth knowing so it is not dismissed as unrelated.
- Find and fix the source before anything is used again. A flue, an appliance, a blocked vent, a bird's nest in a chimney, a generator too close to the house.
- Fit alarms, and read the ventilation page on what an alarm does and does not tell you. In short: at 30 ppm a compliant alarm is required not to sound for two hours, so silence is not evidence of clean air.