Carbon Monoxide Poisoning - The Ultimate Guide! Advice Sheet for Carbon Monoxide Poisoning

 This article will primarily focus on the very real dangers of carbon monoxide (CO) poisoning inherent with the use of any combustible fuel be it fossil fuels such as gas, oil, coal and the use of sustainable biomass fuels such as logs, pellets, wood chip and wood briquettes. The information contained within this article is applicable to all combustible fuel appliances including heaters (installed or portable), stoves, water heaters etc found on boats, campers, mobile homes and even barbeques, and petrol generators, if poorly installed, maintained, and not used in accordance with the manufactures guidelines.


What is Carbon Monoxide?

Carbon Monoxide Poisoning Causes

Carbon Monoxide Poisoning Symptoms

Identifying a Faulty Appliance Emitting Carbon Monoxide

Preventing Carbon Monoxide Exposure

Carbon Monoxide Alarms

What to do if Your Carbon Monoxide Alarm Sounds

The Short and Long Term Effects of Carbon Monoxide Poisoning

The Underreporting of Carbon Monoxide Poisoning

Case Study - Nadine Coyle's Lucky Escape from Carbon Monoxide Poisoning

Helpful Resouces


What is Carbon Monoxide?

Carbon monoxide (1 part carbon to 1 part oxygen) is a poisonous, odourless gas which is produced when fuel is burnt without there being enough oxygen present. It is created by almost anything that burns incompletely. If there is enough oxygen present when fuel is burnt then Carbon Dioxide (1 part carbon to 2 parts oxygen) is produced which is a less harmful gas. You may have heard much about carbon monoxide poisoning recently as it has become a popular issue within the media and has been featured regularly in news and television drama series.


Carbon Monoxide Poisoning Causes

Gas, oil, wood or coal burning appliances along with any other appliance that burn combustible fuels, need plenty of ventilation, that is to say plenty of air, to burn efficiently and safely. Gas appliances just like other appliances burning domestic fuels is a complex chemical reaction producing very little waste other than carbon dioxide (CO2) and water (H2O) in safe amounts. These waste products should be taken away by the flue or chimney. If there is too little air entering the appliance for the gas or fuel to burn completely or if the chimney or flue is blocked, restricted or just plain inadequate either through poor design or mismatched to the appliance then carbon monoxide may be produced and spill back into the living space with potentially devastating consequences.


Carbon Monoxide Poisoning Symptons

The symptoms of Carbon Monoxide poisoning can present themselves in a variety of ways; these are dependent upon the severity of exposure to Carbon Monoxide.

The most common symptom is a Dull Headache, some other symptoms to watch out for are:

  • Weakness

  • Dizziness

  • Nausea or vomiting

  • Shortness of breath

  • Confusion

  • Blurred vision

  • Loss of consciousness

Table 1. below represents the percentage of people diagnosed as suffering from each of the symptoms of Carbon Monoxide poisoning:

Table 1.


 % of diagnosed displaying symptom





 Fatigue or Weakness


 Nausea or Vomiting




 Loss of Consciousness


 Dyspnea (shortness of breath)


 Chest Pain


 Source: Haddad and Winchester's Clinical Management of Poisoning and Drug-Overdose


Other medical clues to carbon monoxide exposure and poisoning you need to be aware of and act upon include similar symptoms if they are being experienced by more than one member of the household? You should ask yourself, do the symptoms disappear when away from home, at work, on holiday or nights away? Does experiencing these symptoms appear to be linked to the use of the heating system, water heater, gas fire or cooker?

 If there are any suspicions that you or any member of the household is experiencing the symptoms of carbon monoxide exposure or poisoning, turn off the appliances within the household, open the windows, get yourself and anybody else outside and seek medical advice from your GP explaining you suspect you have been exposed to Carbon Monoxide. If it is hard to rouse anybody or they have lost consciousness dial 999 immediately.


Symptoms of carbon monoxide poisoning

Image Courtesy of Gas Safe Register


Identifying a Faulty Appliance Emitting Carbon Monoxide

There are two easy identifiable visual warning signs which with a little observance are immediately noticeable that a gas appliance may not be functioning correctly and emitting carbon monoxide. A gas flame should burn with a luminous blue flame. A flame that burns yellow indicates an incomplete combustion of the fuel. The second indication that there may be something wrong with an appliance is the presence of sooty or carbon build ups. These carbon deposits may appear on the canopy or the burners of a fire or on any part of a boiler as sooty deposits or as brown scorch mark like stains. In the case of glass fronted gas fires the carbon deposits may be a little more difficult to see as they will build up at the back of the combustion chamber but a good indication that all is not well is the occurrence of excess or more than usual condensation forming on the glass front or doors. Excessive condensation forming on windows within the room is also an indication that there could be a problem with any type of gas appliance.

The carbon build up is evidence that the initial combustion of the gas is incomplete either due to insufficient oxygen entering the appliance or the failure of the waste products being efficiently evacuated up the flue or chimney. The excess carbon deposits are the waste products of what is in effect an unwanted incomplete 'secondary burn' taking place within the appliance. This incomplete 'secondary burn' of the waste products of combustion can sometimes also be associated with a strange or unusual smell, particularly when igniting the appliance.


Preventing Carbon Monoxide Exposure

  • Do not Obstruct Air Bricks or Ventilation Grilles

  • Use only Qualified Personnel to Install Appliances

  • Get Chimneys and Flues Swept Regularly

  • Keep all Appliances Maintained and Serviced Regularly

  • Fit a Carbon Monoxide Detector

  • Test your Detector once a Week

You must ensure that any air bricks or ventilation grilles are not blocked. It is important other than with balanced flue appliances (but including flueless appliances) that there is plenty of ventilation to allow the fire to burn efficiently, and assist in the carrying away of waste non-combusted products. Sufficient ventilation will also help to prevent the issues associated with depressurisation within a room or property.

With the event of ever increasingly sealed houses through the addition of double glazing can result in more air being consumed by an appliance in the combustion process that is able to enter the room. The effect of this can be two-fold. One insufficient air is available for the complete combustion of the fuel, which will produce CO and prevent the flue system drawing properly with CO potentially spilling into the building. Secondly a depressurised building will 'borrow' air from another inlet such as a central heating or hot water system flue, thus potentially drawing CO into the building. A similar situation can be initiated using an extractor fan in a bathroom or kitchen with the flow of air being drawn directly from the flue or chimney or appliance.

Research carried out by registered engineers revealed that unsafe gas appliances have been found in one in six homes, which is the equivalent of 4.28 million households. At least 68,000 homes escaped from deadly gas incidents in the last year, and around half of the dangerous appliances discovered have been attributed to the fact that people had failed to get

their gas appliance regularly serviced, therefore it had been left in a poor and unsafe condition.

It is essential that all appliances whether gas, oil, mineral or biomass fueled are regularly maintained and serviced. This includes having all flues and chimneys swept. This not only ensures the appliance is burning at its most efficient but will also entail the checking for any potential blockage within a flue or chimney system such a buildup of soot, bird or animal nests etc. A sweep will also be able to check for any leaking flue joints etc. Some of the older oil range type boilers and appliances are fitted with a stabliser at the bottom of the flue system to prevent the drawing of the flame into the flue system by the fluctuation of air pressure within the chimney stem by a gust of wind etc. These at times can cause the leaking of carbon monoxide and other noxious gases to spill into the building and need to be regularly checked and maintained.


Carbon Monoxide Alarms 

Carbon Monoxide alarms are life savers, it is just as important to install one as it is a smoke alarm. It is also now a legal requirement under the regulations  that a Carbon Monoxide alarm is fitted when a new or replacement solid fuel appliance is fitted.  Ideally the alarm should be fitted on the wall or ceiling. If the alarm is fitted to a wall it should be sited as high as possible above any doors and windows but not within 150mm of the ceiling.  If fitted to the ceiling then it must be 300mm away from any wall. Some alarms are also able to be free standing on a shelf or cupboard as long as this is high up in the room. Carbon Monoxide alarms should also be fitted between 1m and 3m horizontally of the appliance. There are exceptions to these rules so please refer to the manufacturers instructions for your particular alarm. Do remember to check your Carbon Monoxide and Smoke alarms at least weekly. There is a great campaign running called Test it Tuesday which encourages everyone to test both CO and smoke alarms every Tuesday, this is a great idea to do as it will help you remember to test all of your detectors. For more help on installing a Carbon Monoxide Alarm see


What to do if Your Carbon Monoxide Alarm Sounds 

So what should you do if the carbon monoxide alarm does go off? The action you take depends on whether or not anybody in the household is experiencing any symptoms of carbon monoxide poisoning or not.


 If the CO alarm sounds and no one in the house have any symptoms:

  • Turn off or extinguish all fuel burning appliances, fires and stoves

  • Move children and infants, pregnant women, the elderly and those suffering from heart or lung conditions out of the home into a safe environment.

  • Open doors and windows to ventilate area

  • Call a qualified gas or oil technician, sweep or fire installer to locate the leak and service your appliance, fire or stove. To find a local technician, installer or sweep use local service provider search

  • Do not use any appliance fire or stove until you get the all clear from the inspecting technician, installer or sweep


 If the CO alarm sounds and one or more people in the household are experiencing possible symptoms:

  • Leave the house immediately do not even stop to silence the alarm

  • Check how many people are experiencing symptoms and what symptoms.

  • Dial the emergency services giving your address, the number of people and what symptoms they are experiencing. DO make sure you tell them you suspect carbon monoxide poisoning and your alarm was triggered.

  • Trust the emergency services if they say you need further medical attention, you do!

  • Under no circumstances re-enter the house without receiving the all clear from the emergency services

  • Have all your appliances, fires and stoves checked by the relevant professional. See local service provider search

  • Ensure all your appliances, stoves and fires are checked, repaired and signed off as fit for use by an appropriately qualified professional before using them again.


The Short and Long Term Effects of Carbon Monoxide Poisoning

Those at greatest risk from the effects of carbon monoxide poisoning are the elderly, pregnant women and their babies, children and those suffering from breathing problems including asthma, bronchitis, emphysema, chronic obstruction of the airways, and cardiovascular diseases.

The short term effects of exposure to low levels of Carbon Monoxide are usually mild, headache is the most common which should gradually ease once away from the affected area. The short term effect of exposure to high concentrations of carbon monoxide can and do result in collapse and death within a few minutes.

The long term effects of prolonged exposure to low levels of carbon monoxide may well display few if any of the classic symptoms and can result in serious long term neurological damage. This can include an inability to concentrate, poor short term memory, problems with short term to long term memory transference, mood swings/emotional instability, and mobility issues.  


The Underreporting of Carbon Monoxide Poisoning

The official statistics tell us accidental carbon monoxide (CO) poisoning accounts for over two hundred people being taken seriously ill requiring hospital treatment and for over fifty deaths a year within England and Wales alone. These figures are highly contested as being a gross under estimate of the true picture and take no account of the number of patients visiting their general practitioner (GP) or local accident and emergency clinics (A & E).

The cost to the NHS of providing treatment for accidental Carbon Monoxide poisoning is estimated to be in the region of £178 million a year. It is well accepted both by industry and healthcare professionals that there is a huge problem with misdiagnosis and in the under reporting of cases. The problem is Carbon Monoxide is colourless, odourless and a tasteless gas which if present in high levels causes drowsiness, coma and eventually death in a relatively short time. The full effects of prolonged exposure to lower concentrations of Carbon Monoxide are not fully understood and further research is needed and ongoing. What is known is that prolonged exposure to quite low levels of CO can cause serious long term neurological damage amongst others.

Whole families who are suffering the ill effects of carbon monoxide poisoning are reporting to their GP's and health care professionals flu like or mild food poisoning symptoms and are subsequently misdiagnosed as such. This is to say nothing of the hidden numbers of the population who do not consult a health care professional in the belief that they just feel a little "under the weather",  tired, stressed, over indulged or was it that dodgy takeaway or slightly past its sell by date tasty treat found at the back of the fridge last night.


Case Study - Nadine Coyle's Lucky Escape from Carbon Monoxide Poisoning

Singer, Nadine Coyle supports Carbon Monoxide - Be Alarmed! the national campaign to reduce the number of deaths and injuries caused by Carbon Monoxide Poisoning. Watch her story of how she became a victim of the silent killer.




 Helpful Resources

Gas Safe Register - - For help with gas appliances.

OFTEC - - For help with oil fired and solid fuel appliances.

HETAS - - For help with solid fuel appliances

HSE - Gas Safety Advice Line 0800 300 363.

National Gas Emergency Service - - 0800 111 999

CO Awareness - - Support for CO poisoning victims and their families


 With thanks to contributors

Sune Nightingale - Stoves Online

Adrian Keats - Proffesional Home Safety from Honeywell

Guy Winterbourne Eco Angus


By Phil Cleaver


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