Today I had my chimneys swept. This is something that needs to be done annually to comply with my house insurance. I don’t often light fires as it is usually fairly warm here but I am hoping to light them over Easter when the house is full of visitors. There is something very comforting about settling down to an after dinner game of Scrabble in front of a roaring fire – even when it is not particularly cold outside.
I burn wood in my fires (rather than coal or peat) and although they work very efficiently there is a build up of unburnt material that settles on the walls of the chimney. This is mostly soot, or carbon; the same stuff that makes a yellow Bunsen flame leave a sooty deposit on glassware in the lab. If it builds up too much it can block the chimney meaning that the fire no longer draws air efficiently. If this happens the fire does not burn well and the fumes that it produces have nowhere else to go.
Worse than the fires not working very well is the risk that the soot will get hot enough within the chimney to catch fire. Also, without a flow of air through the wood burner carbon monoxide gas may be produced. This binds irreversibly with the haemoglobin in your blood causing unpleasant short-term effects and pretty final long-term ones.
My chimney sweep Daniel (known as a ramoneur in France – ramonage means chimney sweeping) wears a respirator to keep the flow of air to his mouth and nose as clean as possible. Dust from the fireplaces could get stuck to his alveoli, reducing their surface area and making his lungs less efficient. He told me that there are sometimes particles so tiny (nanoparticles) that they pass straight through the lungs and into the bloodstream. The filters on his head-gear ensure that the air he breathes is free of soot and other dust particles.
He used a nylon brush on flexible rods attached to a power drill to dislodge the soot that had built up in my chimney over the last year. You can see that some has dropped down into a pile in the photo below. Not much because my fires don’t get used that often – if they were used every day it could be quite a large build up over the year.
The chimney is very important to the success of a fireplace. It has to draw in air over the burning fuel, with the hot air rising up the chimney sucking in cold air from the room by convection. Your room needs to be well ventilated so that the fireplace does not use up all the breathable air. The heat from the fire is conducted through the iron casing of the fireplace and then radiated out into the room. Warm air is also circulated as a result of convection currents rising up from the wood-burning stove.
Ramonage has become a little more sophisticated since the Edwardian era. I was a bit disappointed that Daniel didn’t turn up with a couple of street urchins to send up the chimney – ah, happier times…
Questions…
- What gas from air are my fireplaces using when the wood burns?
- What form of energy does the wood I burn have?
- Wood is mostly hydrocarbons so what two products would you expect to be produced when it burns completely?
- What two gases are normally transported around the body by the haemoglobin in your red blood cells?
- What three forms of heat transfer do I refer to in the article above?
- I mentioned two fossil fuels. What are they and suggest two other examples of fossil fuels?
How they clean chimneys in Russia – just set your leaf blower to suck rather than blow, apparently…
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