What is carbon monoxide?
Carbon monoxide is a poisonous gas. It can be given off by appliances
that burn fossil fuels such as gas, coal, wood or oil, if they're
not working properly, if the flue is blocked in any way, or if
the room is not properly ventilated.
Why is it so dangerous?
Carbon monoxide is odourless, colourless and tasteless, which
makes it difficult to detect. However, its effects are deadly.
On average, 50 people a year are killed by carbon monoxide poisoning
due to faulty heating appliances.
What are the main causes of carbon monoxide poisoning?
Most cases of carbon monoxide poisoning are due to inadequate
ventilation or poor maintenance of appliances, blocked or leaky
flues and chimneys. Chimneys can become blocked for various reasons.
It could be as a result of birds nesting on the chimney, or possible
degradation of the flue. A blocked flue can lead to carbon monoxide
leaking into your home.
Who is most at risk?
Some people mistakenly think that it is only gas-fuelled heating
systems which can cause carbon monoxide poisoning - in fact,
it can happen with any fossil fuel system if the system, which
includes both the appliance and the flue, is faulty or the room
is not properly ventilated. Also, some people associate carbon
monoxide poisoning with rented accommodation - in fact, more
people are killed in owner-occupied rather than rented properties.
In the period 1989-1998 there were 533 deaths from carbon
monoxide poisoning in the UK:
- 438 in England and Wales
- 46 in Scotland
- 49 in Northern Ireland
Fuels involved in carbon monoxide poisoning accidents
Type of appliance involved (all accidents)
Cause of fatal accidents
Age distribution of victims
Carbon monoxide poisoning
A typical scenario is a living room with a solid fuel heater.
The windows and doors have been draught-proofed and the permanent
ventilation has been blocked up (by the victim) to prevent draughts.
The chimney and flue have not been swept for years. The victim
may not have carried out the regular maintenance of their appliance,
like cleaning the throat plate monthly, let alone had the appliance
serviced professionally. There may be soot deposits at the appliance
outlet, or bits of the flue lining may have broken away and tumbled
down to the appliance outlet. The weather is cold and the fire
is not drawing well, so the victim opens the fire door to get
more heat. This compounds the problem. The victim becomes drowsy,
falls asleep, and doesn't wake up again.
Table 1 Regional variation of deaths from poisoning
by carbon monoxide from domestic heating appliances (1989-1998)
number of Cases 1989 to 1998
Death Rate per 100m Population per YearPopulation (m)
Rates take no account of relative use of gas and non-gas appliances
Gas includes bottled gas
Source: Metra Martech
Note on interpretation of the figures
Northern Ireland has 275/90 times = 3.06 times national average death rate
(roughly 3 times)
Wales has 217/90 times = 2.41 times national average death rate (roughly 21/2
West Midlands has 101/90 times 8 approximately 10% higher than national average
Table 2 Seasonal fluctuation of fatal poisoning by carbon
monoxide from malfunctioning domestic appliances
Source: Metra Martech
- General awareness of the danger of carbon monoxide is reasonably
high among the general public, but practical and specific knowledge
- Awareness is largely limited to gas - very few people associate
carbon monoxide with other fossil fuels. Over half (56 per
cent) think that a coal fire cannot cause carbon monoxide poisoning,
or simply do not know.
- One in ten people cannot name any potential sources of carbon
monoxide in their home.
- Just one in four (27 per cent) is aware that poor ventilation
can result in a build-up of carbon monoxide.
- Over one in three do not know what colour a flame on a gas
boiler will burn if there are traces of carbon monoxide (orange
or yellow). One in twenty thinks that it actually should burn
orange or yellow, rather than blue.
People do not necessarily take the recommended safety precautions
to reduce the risk of carbon monoxide poisoning in their home:
- Three in ten households with a gas boiler or heating system
have not had it serviced in the last year. This is a particular
problem among owner-occupiers.
- Just one in five households (22 per cent) with a chimney
in use has had it swept in the last year, and 58 per cent have
not done so in the last four years, including 8 per cent who
have never had it swept.
Key safety messages: the danger signs
Carbon monoxide may be present if there are any of the following
- Gas flames that normally burn blue burn orange or yellow
- Sooty stains appear on or just above appliances, regardless
of the fuel being burnt.
- Coal or wood fires burn slowly or go out.
- The fire is difficult to light.
- The room is not properly ventilated.
- The chimney or flue is blocked - watch out for smoke in the
room. Look out for masonry debris in the grate or appliance.
- You develop the following unexplained symptoms:
- chest pains
Good practice guidelines
Given that accurate knowledge of the hazards of carbon monoxide
is so low, it is important to communicate relevant information,
so that people know the risks involved and the consequences of
not taking the necessary safety precautions.
- Carbon monoxide can result from burning all fossil fuels
- not just gas fires and boilers.
- It is important to ensure rooms are ventilated - never block
vents. If double-glazing or draught-proofing is fitted, make
sure there is still enough air circulating for any heaters
in the room.
- Portable heaters do not need a flue, but they still need
- Make sure that all chimneys and flues are regularly swept
by a competent sweep_(i.e. a member of the National Association_of
Chimney Sweeps), and kept clear. This includes chimneys being
used as flues for gas fires, but it is particularly important
for solid fuel appliances.
- Boilers and heating systems and appliances should be installed,
maintained and regularly serviced by a competent engineer (make
sure they are CORGI-registered for gas appliances; HETAS-registered
for solid fuel appliances; or OFTEC-registered for oil-burning
- If you have recently moved, check when your boiler or heating
appliances were last serviced.
- Gas flames burning orange or yellow instead of blue may indicate
the presence of carbon monoxide.
- Carbon monoxide detectors should comply with British Standard
BS 7860 - but remember they are only warning devices. Never
rely on them entirely and do not use them as a substitute for
- Never cook on a barbecue indoors - the charcoal gives off
- If you develop any of the following unexplained symptoms
- drowsiness, headaches, chest pains, giddiness, sickness,
diarrhoea, stomach pains - you could be suffering from carbon
monoxide poisoning. Switch off your appliances and see your
doctor at once.