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What causes Carbon Monoxide poisoning?

What Carbon Monoxide is, what the dangers are and what to do in an emergency or if you suspect Carbon Monoxide poisoning.

Most cases of carbon monoxide poisoning are because of poor ventilation or maintenance of appliances, blocked or leaky flues and chimneys.  

A blocked chimney or flue can lead to carbon monoxide leaking into your home.

What are the dangers of carbon monoxide?

Carbon monoxide is a dangerous gas which can cause serious illness or even kill. It is difficult to detect as you can’t see it, smell it or taste it. Even low levels of this poisonous gas can cause brain damage or death.

Be aware of:

  • yellow or brown staining / soot deposits on or around appliances regardless of the fuel being burnt;
  • fires that are difficult to light;
  • coal or wood fires burning slowly or going out;
  • smoke in a room - the chimney or flue could be blocked;
  • pilot lights that often blow out;
  • increased condensation inside windows; and / or
  • gas flames which are orange or yellow when they are normally blue.


Mild carbon monoxide poisoning

Headaches, nausea, vomiting, drowsiness, poor co-ordination.

Moderate or severe carbon monoxide poisoning

Symptoms – confusion, unconsciousness, chest pain, shortness of breath, coma, death.

Most people who develop mild carbon monoxide poisoning recover quickly when moved into fresh air. In cases of severe carbon monoxide poisoning people are often unable to move and must be rescued.

Severe poisoning is often fatal. Victims may not recognise drowsiness as a symptom of poisoning, fall asleep and not wake up again.

If you or your family experience any of these symptoms and believe that carbon monoxide could be responsible, you should contact the

National gas emergency number - 0800 111 999 and seek medical advice immediately.

How do I recognise there is a problem?

  • More than one person in the house with the same symptoms.
  • Health improves when away from home and reappears on their return.
  • Symptoms may be more noticeable when cooking if it is a fault with the oven.
  • May be more noticeable in the colder months if it is a problem with the heating.

What do I do in an emergency?

  • Move the affected person into the fresh air.
  • Get medical help.
  • If the person is not breathing, perform artificial respiration until help arrives.

Confirming carbon monoxide poisoning.

Because the symptoms are common ones carbon monoxide can be hard to diagnose. If you suspect it could be a possibility tell the doctor of the events surrounding your illness. The only way to confirm carbon monoxide poisoning is a specialised test.

Key facts and safety advice about carbon monoxide

  • Carbon monoxide can result from burning wood, coal, coke, charcoal and other fossil fuels - not just gas fires and boilers.
  • Make sure rooms are aired - never block air vents.  If double glazing or draught proofing is fitted, make sure there is still enough air circulating.
  • Portable heaters must not be used.
  • Chimneys and flues should be swept regularly and kept clear.  This includes chimneys being used as flues for gas fires, but is important for solid fuel appliances.  Under your tenancy agreement, if you have a solid fuel appliance it is your responsibility to get the chimney swept regularly by a registered chimney sweep.  (Check the Yellow Pages or your local newspaper for adverts.)
  • Boilers, heating systems and appliances should be maintained regularly.  If your gas appliances are serviced every 12 months in accordance with your Tenancy Agreement, the risk of Carbon Monoxide is reduced and your gas appliances are more efficient.
  • Never cook on a barbeque indoors - the charcoal produces carbon monoxide.
  • Tenants should only sleep in bedrooms and not rooms where gas appliances are installed. 

If a room with a gas appliance must be used to sleep in, please contact OneCALL on 0345 8 507 507 for further advice.

Important: The Carbon monoxide detectors are only an alarm, you must allow our engineers into your home to carry out the annual gas service as stated in your Tenancy Agreement. Never rely on Carbon monoxide detectors.

WDH is committed to your safety and insist that all appliances are serviced every 12 months. As your landlord we will ensure the following.

  • Gas fittings and flues installed / owned by WDH are maintained and in a safe condition.
  • All installations, maintenance and gas servicing is carried out by a Gas Safe registered engineers.
  • Any flues or chimneys are checked when we carry out your gas appliances’ annual service. We will not service or repair gas cookers.
  • We keep a copy of each annual gas service.
  • You get a copy of the current gas safety certificate for your home when completed. If you are a new tenant, a copy will be in your tenancy pack.
  • All our gas engineers will carry a WDH ID badge and a Gas Safe photograph ID card. Always ask for proof of WDH identity before you let them into your home.
  • We contact you when your appliances are due for an annual gas service and advise you of an appointment date.

As a WDH tenant you too have responsibilities.

  • You should allow us access to your home to carry out maintenance and safety checks on our gas appliances, as stated in your tenancy agreement.
  • You must let authorised employees of WDH, or other agents, into your home at all reasonable hours to carry out any inspections or any work
    we consider necessary. This is to ensure the property and surrounding properties do not put you or anyone else at risk. We will give you 24 hours advance notice in writing, if possible.
  • If you want to replace a gas appliance, always seek permission from us first. Call OneCALL on
    0345 8 507 507.
  • Never use an appliance if you think it is not working properly. Report it to OneCALL on 0345 8 507 507.
  • Never cover an appliance or block / obstruct any convection air vents, fixed ventilation grilles or airbricks.
  • Always follow the manufacturers’ instructions when using appliances.



gas safety ; safety check ; carbon monoxide check ; Drowsy; sleepy; tired; sick; headache; nausea