Many of us long for a roaring, open fire but, if you’re lucky enough to have one, you’ll understand that they aren’t all cosy evenings and romantic winter days – they also need plenty of upkeep and maintenance to ensure that they can function efficiently and safely. But it can be difficult to know if your chimney is blocked, and how to prevent it from happening…

What can cause a chimney blockage?

There are three main causes of chimney blockages:

  • An excessive build-up of soot or creosote (tar)
  • Birds, squirrels, or other small animals nesting in the chimney
  • The collapse of the internal chimney bricks 

According to Peter Harris, of Wilkins Chimney Sweep, who is a member of the APICS (The Association of Professional and Independent Chimney Sweeps), an HETAS Approved Chimney Sweep, and serves on the Steering Committee of APICS, the collapse of the internal chimney bricks is far less common than the other two ways, occurring when the internal bricks fall inwards and block the chimney. 'If this happens when a fire is not lit, then there should be little damage to the fireplace. However, if the fire is lit, fumes and smoke may be prevented from escaping up the chimney. If this happens, then the fire should be extinguished immediately and the doors and windows should be opened to ventilate the room.'

Signs your chimney is becoming blocked

Peter told us: 'Unfortunately, there are very few signs that a chimney is becoming blocked, other than smoke or fumes entering the room. This can lead to carbon monoxide poisoning, which is highly dangerous as it could result in illness or, in extreme cases, death. Soot dropping into the fireplace is another sign that your chimney is due a sweep.'

You should also keep an eye out for nesting material. If a bird or small animal has chosen your chimney to nest in, you will start to see evidence of nesting material falling down the chimney. If you notice twigs or other material coming down the chimney, this is probably an early indication of nesting activity – so don’t ignore it.

How to prevent your chimney getting blocked

Sweep it regularly - according to Peter, to ensure that your chimney doesn’t  become blocked by soot or other deposits as a result of burning, “it’s vital that you have the chimney swept at least once a year by a qualified chimney sweep. Woodburner flues, especially lined ones, generally need sweeping more frequently, with the fire service recommending that they are swept every three months when in use”.

Bird proof your chimney - if you notice the early signs of a bird or small animal nesting in your chimney, its important to act quickly! You should have a bird proof guard or cowl fitted to the chimney straight away. If you have your chimney regularly swept (and you should!), it’s important to ensure that your guard is one that is physically attached to the chimney, rather than one that simply drops in as these tend to be pushed out when the chimney is swept.

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