Your stove itself is not the problem! This is what Hetas have to say: Properly installed, operated and maintained your stove should not emit fumes into the dwelling. Occasional fumes from removing ash and refuelling may occur, however persistent fume emission is dangerous and must not be tolerated. They recommend the following immediate action:
• Open doors and windows to provide ventilation – then leave the premises
• Let the fire go out
• When the stove is cold, check for a blockage in he stove's flueway area and clean if required. As an additional precaution also have your chimney swept
• Under no circumstances attempt to relight the fire until the cause of the smoke emission has been identified (see other causes below) and corrected – if necessary seek expert advice
From The Stove Yard's experience the most common cause of smoke and fume emission is a blockage in the flueway (that's the area in the roof of the stove above the baffle plate) or chimney / flue system due to a lack of basic routine maintenance. Stove owners who don't regularly check the flueway or have their chimney swept are putting themselves and their families in danger.
Photographs show a dangerously blocked flueway. The pound coin is positioned to indicate the extent of the blockage and to show what little remains of the flue gas passageway. Neglecting the flueway like this poses a serious threat to lives.
Keeping the flueway and baffle plate clear
In most modern stoves the 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). For most stoves all you need to do is to remove the fire fence (aka log bars) at the front of the stove to provide easy access. Next remove one of the two side firebricks which help keep the baffle plate (aka throat plate) in the roof of the stove. On older stoves there may be a couple of brackets at the top of the side firebricks that help keep them and the baffle plate in place. 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, use 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 indicate that you are burning wood which has a higher moisture content than is recommended and you should immediately review the quality of your wood fuel. Please note that burning wet or unseasoned wood in a Defra Smoke Exempted Appliance in a Smoke Control Area is illegal as it will contravene the terms of the appliance's operation and exemption ie only to burn logs with a moisture content of less than 20%.
Removing a baffle. After removing the fire fence and one of the side firebricks, push the baffle upwards, then drop it down at an angle to manoeuvre from fire chamber. Remember the baffle will probably be very heavy.
Here's some other reasons, either alone or combined, which could cause a stove to emit smoke into the room
• Inadequate supply of combustion air
Check that any permanent air vent to supply the extra combustion air required for the stove, normally fitted to comply with building regulations, has not been accidentally blocked. Some stove manufacturers and building regulations prohibit the use of a stove in the same room as an extractor fan and in order to overcome this restriction a direct air supply is sometimes used to deliver the combustion air directly to the stove from the outside. The direct air inlet should therefore also be checked for blockages. 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 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.
• Extreme weather conditions
High winds or temperature extremes can sometimes temporarily affect the stove's performance. At The stove Yard we can 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 up-draught. 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.
• 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.
• 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. 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.
• Insufficient flue height (or a flue that is very tall)
The minimum flue height required by most stove manufacturer's, 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 up-draught to safely remove the flue gases and this will then be very quickly exacerbated during adverse weather.
Stove installations with taller than average (say 12 metres-plus) 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 up-draught to remove the smoke. Ensuring that any exposed chimney is kept warm by providing the appropriate insulation with a flue liner, which has also been back-filled with vermiculite, 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 another chimney expert.
• 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 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.