‘Native wood is an ecological fuel, but only if certain rules are observed when lighting it,’ explains Jonas Wieland, from Alpnach in Obwalden. Wieland can boast the fascinating title of ‘master chimney sweep’, and is also president of the Swiss Association of Combustion Plant Inspectors (ASCC).
If the fire is lit correctly, ‘a wood heating system produces practically no smoke, which is the cause of the problems’. The effect of a fire that is not lit properly is clearly visible on winter days, when stable pockets of cold air form in lowland towns and trap exhaust gases and pollutants. The smoke from chimneys then spreads like a kind of veil over the built-up areas and forms a veritable fog.
It is in this ‘veil’, which might even look picturesque, that large quantities of harmful substances are in fact contained: chiefly polycyclic aromatic hydrocarbons (PAHs), whose carcinogenicity is proven, and the fine particulates that we unfortunately know all too well, but whose harmful effects on human beings, such as the development of tumours and other diseases, we still struggle to take seriously. By now we should all know that the most dangerous of these are particles with a diameter of less than 2.5 micrometres (so-called Particulate Matter, PM2.5), which enter the bloodstream through the lungs.
Switzerland has long been committed to reducing fine particulate emissions. And, since the Swiss are in the habit of doing things seriously, it has achieved good results. Between 1990 and 2019, annual PM2.5 emissions from wood-burning installations in Switzerland fell from about 5,400 tonnes to 1,500 tonnes.
According to master chimney sweep Wieland, more can be done. Starting with wood-burning appliances for heating individual rooms. ‘Larger boiler heating systems are generally fully or largely automatic,’ he explains. ‘With open fireplaces or tiled stoves, things are different.’
At the Bern University of Applied Sciences (BFH) in Biel, where trainee combustion plant inspectors are taught, Wieland uses practical demonstrations to teach the correct lighting method. ‘In an optimal combustion process, practically only water vapour and CO2 are produced. All that remains of the wood is very fine ash.’
To achieve this, it is essential that the logs are dry and placed close together in the combustion chamber. On top goes the lighting module: four thin fir logs arranged in a cross. In the centre, a handful of wood shavings soaked in wax are placed. Once the fire is lit, the fir logs will burn first and then the firewood beneath them.
The secret is all here, simple and ultimately little more than intuitive: use dry, natural logs that are not too thick, arrange them in the way described, light the fire from the top, and keep the draught regulator and the chimney damper open while lighting. In this way the smoke disappears within a few minutes, absorbed by the flames.
‘If, on the other hand, the fire is lit from below, or if the logs are too damp or too thick, or if the fire is not hot enough because of an inadequate air supply, a large amount of smoke is produced and released from the chimney into the outside environment.’
In all this, the role of the master chimney sweep is very important. ‘When I am called to clean a stove, I can tell from the soot deposits and the ash residues whether the fire was lit incorrectly or even whether rubbish has been burnt’, which is utterly wrong and absolutely to be avoided for obvious reasons. ‘At that point,’ says Wieland, ‘I try to find out from the customer which fuel they use, how they light the fire and how they regulate the air supply. I don’t want to play the policeman, only to explain the advantages of lighting the fire correctly.’
It is also a question of psychology, after all. ‘I can’t simply tell someone who has been lighting the fire the same way for years that they are doing everything wrong.’ And it is still a matter of ‘entering’, physically too, the intimacy of private homes, and we all know how jealous each of us is of our own domestic freedom.
Newcomers to wood heating are more willing to accept the ‘lesson’. To convince the self-styled professionals (a bit like when lighting barbecues…) a little tact is needed: ‘Generally, you succeed in the end by pointing out that everything that comes out of the chimney settles again around the house. Those who do not follow the correct practices poison the surrounding environment and the air they breathe.’
Moreover, it is not just a matter of well-meant advice. In 2018 the Swiss Confederation introduced limit values for fine particulate and carbon monoxide emissions even for wood-burning installations with a nominal output of up to 70 kilowatts. Incorrect lighting is therefore a genuine offence. During regular operation, the Air Pollution Control Ordinance (OIAt) provides for periodic spot checks; some cantons also require an ash inspection.
This is why Swiss chimney sweeps also work as combustion plant inspectors, and their inspection role is decisive. To this end, the FOEN, the Swiss Federal Office for the Environment, has launched the ‘Point of Fire’ campaign, which gives professionals numerous suggestions on how to steer their customers effectively towards correct lighting methods.
At the end of Wieland’s demonstration, only a thin layer of white ash remained in the stove’s combustion chamber. It is proof that the wood has burnt completely, producing very little smoke. ‘It’s a good feeling to do things the right way and to have the situation under control. When it comes to lighting a fire, nothing beats wood for me.’ And so, long live the chimney sweep.
