How to keep the flueway and baffle plate clear of potential blockages

In most modern stoves manufacturers have recognised the importance of this safety procedure and have made it as simple as possible to carry it out – although it can be quite messy, so protect decorative and porous surfaces (and your lungs). If you have access to the manufacturer's handbook always follow their instructions.

In the absence of the stove's handbook the following method will usually work. For most stoves all you need to do is to remove the fire fence at the front of the firebed to help provide easier access. Next remove one of the two side firebricks which will normally keep the baffle plate in place in the roof of the firechamber. On some older stoves there may also be a loose-fitting metal bracket at the top of the firebrick that helps keep both the firebrick and baffle plate in position. Once the firebrick has been removed this will enable you to push the baffle upwards and then to drop it downwards and angle it to remove it from the fire chamber. Make a note of the exact way that the baffle came out (or take a photo, just to be sure). Clean the entrance to the flue pipe thoroughly, and remove any caked soot from the baffle plate, using a wire brush if necessary.

If your flue pipe has an inspection hatch, also examine that. If there is an excessive amount of soot here as well as around the flueway then you should also have your chimney swept as this could be an indication of the general state of the rest of your flue system. If the soot has an acrid smell and is caked or tarry then this would further indicate that you are burning wet wood which has a higher moisture content than is recommended and you should immediately review the quality of your wood fuel. Please Note: Burning wet or unseasoned wood in a Defra Smoke Exempted Appliance will cause excessive and unnecessary smoke which is is illegal and will contravene the terms of the appliance's operation and official smoke exemption ie that the stove is permitted only to burn logs with a moisture content of less than 20%.

Here's some other reasons, either alone or combined, which could cause a stove to emit smoke into the room

1. Inadequate supply of combustion air

Check that any permanent air vent to supply the extra combustion air required for the stove, to comply with building regulations, has not been accidentally blocked. This is normally fitted on a wall near the floor close to the stove. Where a stove has been fitted in a living space which has an extractor fan (eg kitchen diner) a direct external air supply inlet will typically have been fitted on the outside wall behind the stove and this should therefore also be checked outside for blockages such as leaves or snow drifts. 

One easy way to determine if your stove is receiving enough combustion air, even if the stove doesn't have a dedicated air vent, is to simply open a window in the same room as the stove whilst the stove is under fire (turn on the extractor fan if you have one). If the smoke then dissipates then you should consult the original installer or seek other expert advice, and certainly not use your stove until the problem has been rectified.

2. Extreme weather conditions

High winds or temperature extremes can sometimes temporarily affect the stove's performance. At The stove Yard we can always guarantee a number of telephone calls during such weather conditions – usually opening with 'the stove's stopped working, there's smoke in the room'. Typically, it's either an unusually hot day or a cold snap in the Autumn or Spring which upsets the normal pressure differences between the flue / room and the outside air to create the required updraught. In the case of freezing temperatures, when the outside air is much colder and therefore heavier than normal, you should always build a much bigger than usual kindling pre-fire to provide a strong blast of heat in the fire chamber to warm the chimney and 'reset' the flue draught pressure. After this, only use the faster-burning smaller logs until the fire is firmly established.

Unusually hot sunny days can produce negative pressure in the flue. This is where the room pressure and temperature are much less than that of the outside air and this can sometimes make the fire harder to light and also cause smoke to enter the room. This can easily be rectified by opening a window (or door) to the outside which is in the same room as the stove. This will re-balance the air pressure. Once the up-draught is working again and the fire is burning well you can close the window or door. If the stove starts to emit smoke into the room again, then please read the sections above, particularly about cleaning the flueway.

3. High winds

High winds whipping across the top of the chimney terminal can sometimes create a 'flute-like' effect making it difficult for the flue gases to exit the system so that they are then emitted into the room. If this is a persistent problem, particularly with a strong prevailing wind, you may need to fit a specialist chimney cowl which has been designed to provide a stable draught. These can be expensive so it is always best to seek specialist advice to ensure that the correct cowl is selected and that it will provide a permanent solution to your particular problem.

4. Changes to the area around the flue exit

If your stove has performed well in the previous season and has suddenly started smoking when you start to use it again – and you've checked that the flueway is clear (see above), you should then also check that any trees near the top of your chimney haven't grown during the summer to affect the free movement of the flue gases as they exit. In such cases the tree canopy should be trimmed back. The close proximity of any new buildings or extensions, especially if they're taller, could also affect the performance of your flue system. In such cases you should consult a stove installer to re-calculate the height of the flue system so that it can be increased to bring it back into line with Building Regulations requirements and will work. Finally, you'd be surprised how often a bird's nest can be at the route of the problem, so ensure that your chimney is regularly swept at the beginning or end of each heating season. You may need to fit a new cowl which incorporates a bird guard to prevent a re-occurence.

5. Insufficient flue height (or a flue that is very tall)

The minimum flue height required by most stove manufacturers, as well as Building Regulations, is 4.5 metres (15') from the top of the stove. Flues that do not comply with this minimum height will generally have problems in delivering sufficient updraught to safely remove the flue gases and this will then be very quickly exacerbated during adverse weather.

Stove installations with taller than average flue systems can also be susceptible to smoke emission into the room, especially if the chimney is on the outside of the building and it is also subject to a cold prevailing wind. This is because the flue gas gets cooled and becomes heavier the higher up in the flue it gets to the point where the flue pressure just isn't sufficient to create the required updraught to allow the smoke to exit the chimney. Ensuring that any exposed chimney is kept warm by providing the appropriate insulation with a flue liner, which may also need to be back-filled with vermiculite or wrapped with suitable chimney liner insulation, would certainly help minimise such issues. Alternatively, whether it's a short or tall flue system, and only after consulting a chimney expert, some form of specialised anti-downdraught cowl or mechanical extraction may also be required to maintain a safe up-draught

If you think that this is the problem then consult the original stove installer or other chimney expert.

6. A 'cold' chimney

For smoke to travel up the chimney, it is crucial for the chimney and flue system to be warm. Smoke will only travel upwards if it is lighter than air – and it can only be lighter if it is actually kept warmer than the outside air. So if you don't have an insulated chimney to keep the flue gases as warm as possible, especially if the chimney is on outside wall, then you may experience slow to light fires and problems with smoke both of which will be made worse when it is particularly cold outside.