Carbon monoxide (CO) is a colourless, odourless gas from which older people, children, pregnant women and those with breathing problems or cardiovascular disease are at increased risk.
CO is not just produced by malfunctioning or poorly flued gas appliances but by the incomplete combustion of all carbon-containing fuels: gas (domestic or bottled), coal, coke, oil, biofuel and wood. Stoves, fires and boilers, water heaters, paraffin heaters and room heaters are all potential sources. Caravans, boats and mobile homes with portable devices using these fuels are also potential sites of exposure. Exhaust gasses from vehicle engines, diesel and petrol powered electricity generators and BBQs can also contain or emit high levels of CO.
Signs and symptoms
Recognising CO poisoning is not at all easy as it may simulate many other conditions like influenza or food poisoning.
The onset of symptoms is often insidious and may not be recognised by either the patient or the health adviser. The commonest symptoms and signs and an indication of their approximate frequency in CO poisoning are shown below:
- Headache 90 per cent
- Nausea and vomiting 50 per cent
- Vertigo 50 per cent
- Alteration in consciousness 30 per cent
- Subjective weakness 20 per cent
What look like classic cases of food poisoning of a whole family may be produced by carbon monoxide poisoning. Prolonged exposure to concentrations that produce only minor symptoms may, in some cases, be associated with lasting neurological effects. These include difficulties in concentrating and emotional ability.
There are four key questions that should be asked to help diagnose domestic carbon monoxide poisoning. These questions can be remembered using the acronym COMA:
C for Co-habitees and co-occupants - is anyone else in the house affected (including pets)?
O for Outdoors - do your symptoms improve when out of the house?
M for Maintenance - are heating and cooking appliances properly maintained?
A for Alarm – do you have a carbon monoxide alarm?
The answers given for each question should raise or lower suspicion of poisoning by carbon monoxide.
The following signs may be recognised in the home:
- black sooty staining on or around an appliance (e.g. stoves, boilers and fires) such as on the walls
- smoke or excessive condensation accumulating in rooms due to faulty flues: though you cannot smell carbon monoxide, you can often smell other combustion products
- yellow or orange, instead of blue, flames from gas appliances or boiler pilot lights