Carbon monoxide


Find out about the dangers from carbon monoxide and how best to protect yourself and others from this deadly gas.

'Silent killer'

CO is produced by the incomplete combustion of solid, liquid, and gaseous fuels. It is a highly poisonous gas which is impossible to see, taste or smell and is often known as the ‘silent killer’. 

Under normal circumstances, CO should not be detectable in the typical home or workplace. When appliances are kept in good working condition, they produce little CO.

Watchout Carbon Monoxide Kills logo Watchout - Carbon Monoxide Kills

'Watchout Carbon Monoxide Kills' is a campaign developed by the Northern Ireland CO Safety Group to raise awareness about the dangers of deadly CO.

Every November the group also promotes awareness about CO through its Carbon Monoxide Awareness Month.

Sources of CO

Most homes and businesses use appliances that burn fuels such as gas, oil and coal, peat and wood.

If these appliances are not installed, maintained, and used properly, carbon monoxide (CO) can build up to dangerous and even deadly levels, particularly in poorly ventilated areas.

Using kerosene heaters or charcoal grills indoors, or running a car in a garage, can also cause levels high enough to result in CO poisoning.

Common sources of CO include the following wood, oil or gas-fuelled appliances:

  • boilers
  • room heaters
  • furnaces
  • charcoal grills
  • cooking ranges
  • water heaters
  • vehicles run in closed garages
  • fireplaces
  • portable generators
  • wood-burning stoves

Appliances such as electrical heaters, electric water heaters and toasters do not produce CO under any circumstances.

Best protection

The best way to protect against carbon monoxide is to make sure all fuel-burning appliances are properly installed by recognised and established engineers, and serviced by competent companies or individuals - at least once a year.

Always follow the manufacturer's instructions for boilers, stoves, gas fires and solid fuel room heaters.

Don’t forget that chimneys and flues should also be inspected annually and swept, if required, by a registered technician.

CO alarms

As a back-up measure, you should also install an audible carbon monoxide alarm – these are widely available to buy from supermarkets, DIY stores or online retailers.

Some of you may have CO alarms fitted in your home for a number of years now. However, CO alarms have a limited life span, so please check yours to see if it is working properly. It might be time to buy a new one.

Remember, while carbon monoxide alarms can help alert you to the dangers if CO gas escapes, they must never be regarded as a substitute for the proper installation, maintenance, servicing and cleaning of appliances that use gas, coal, oil or any other solid fuel.

Carbon monoxide alarms are a mandatory requirement for all new homes built in Northern Ireland after a change to The Building Regulations (Northern Ireland) 2012 came into operation on 31 October 2012.

New solid fuel appliances

Before installing a new solid fuel appliance, or relining or installing flues and chimneys for these appliances, it is a legal requirement to submit an application for building regulation approval.

Contact your local council’s building control department before you start this work.

Away from home

We normally associate CO with domestic fossil-fuel burning appliances and most of us are aware of its dangers in the home.

However, incidents and fatalities relating to CO can also occur in holiday homes, caravans and on board boats where faulty gas cookers, appliances or petrol-powered generators have led to carbon monoxide poisoning. So, make sure all appliances are properly installed and are serviced regularly.

Carbon Monoxide poisoning can also occur when people bring gas and charcoal BBQs into tents and other small enclosed spaces, sometimes in an attempt to keep warm.


Early symptoms of Carbon Monoxide (CO) poisoning can mimic many common ailments and may easily be confused with food poisoning, viral infections, flu or simple tiredness.

Exposure to high concentration levels of CO, even for a short time, can render a person gradually becoming unconscious.  Unfortunately many people do not recover from the unconscious phase.

Symptoms to look out for include:

  • headache
  • nausea
  • breathlessness
  • dizziness
  • collapse
  • unconsciousness

What to do in an emergency

TASK magnet image If you suspect carbon monoxide is present remember follow the ‘TASK’  checklist:

  • turn off or extinguish the heating source/appliance if safe to do so
  • air - ventilate your home by opening windows and doors, stay outside in the fresh air
  • seek medical help if you feel unwell
  • keep all heating sources/appliances off until serviced (or chimney/flues cleaned) by a qualified professional

If you or your family experience any of the above symptoms and you believe CO may be involved, you must seek urgent medical advice from either your doctor or an accident and emergency department.

You should ask for a blood or breath test to confirm the presence of CO. Be aware, CO quickly leaves the blood and tests may be inaccurate if taken more than four hours after exposure has ceased.

Detailed health information for carbon monoxide is available from the Public Health Agency.

Emergency service contacts

Gas - contact NI Gas Emergency Service (24 hours) 

  • phone: 0800 002 001

Oil - contact OFTEC

Landlord/Tenant Responsibilities

Landlords and tenants both have responsibilities to ensure the safety of their premises.

When it comes to carbon monoxide safety and the law, it depends on what type of fuel you have. More detailed factsheets are available below but as a general rule:

Landlords are always responsible for gas and electrical appliances
A tenancy agreement can stipulate repairing responsibilities
Repairs must be carried out within a reasonable time.


Information leaflets



A TV advert was developed as part of the HSENI 'Watch Out. Carbon Monoxide Kills' campaign to raise awareness of the risk of carbon monoxide poisoning.

You can view the advert on HSENI's YouTube channel.

A student video was also developed as part of the HSENI 'Watch Out. Carbon Monoxide Kills' campaign, which aims to raise awareness of the risk of Carbon Monoxide poisoning amongst the Northern Ireland population.

Key legislation

Please note that these links are to the original legislation, visitors should verify for themselves whether legislation is in force or whether it has been amended or repealed by subsequent legislation.