Green Oversite



Wood Smoke

A Health Hazard

Wood smoke is a health hazard. It is that clear and simple. However unfortunately the problems associated with wood smoke are unrecognised by a large section of society.

The reason for this lack of recognition is most likely that there has been no education within the community of the health problems associated with wood smoke. Wood fires for heating, the main source of urban and semi-rural wood smoke, has developed a "romantic" image of the roaring fire in the house churning out loads of heat. There are images of sitting in front of the fire watching the flames. Some people even think that wood smoke smells good - I think it smells like what it is - pollution. Wood fires have also gained an image of being "environmentally friendly" because the wood that is burnt is seen as a renewable resource. This is often a false perception.

It surprises me how little recognised the problem of wood smoke is. Cigarette smoking is now recognised as a major health risk - you would be hard pressed to find anybody in Australia who at least has not heard the health warning (even though some may be stubbornly in denial about the effect on themselves). It has even been recognised about the effect of cigarette smoke on people near the smoker who may breathe in exhaled cigarette smoke - passive smoking. Consequently smoking has been banned from public places such as offices and hotel bars due to adverse health effects on people other than the smoker themself. Smoking has even been banned from places which are largely outside, such as sporting arenas and undercover areas on railway platforms. While I am not saying that the health risk from wood smoke are exactly the same as cigarette smoke - I am not a doctor nor scientist - it is logical to me that the health problems arising from wood smoke would have many similarities to cigarette smoke. Smoke is smoke. The "ingredients" of smoke from any source have similarities, the health risks have similarities. Consequently breathing wood smoke from a neighbours' wood fire or your own probably has health risks which may be similar to breathing in "passive" cigarette smoke.

Cigarette Wood Smoke Comparison

Wood smoke does not have to be visible to be a health risk - although it often can be seen - coming out of chimneys and as a general haze of pollution in the air. If you can smell it in the air then there is a greater health risk than with clean air. What’s the use of pollution control on cars, banning cigarette smoking in public places, when the wood smoke polluted air fills your lungs with particle and chemical pollution anyway?

Wood smoke is a major source of air pollution in urban and semi rural settings. For example in Sydney only 13% of the houses use wood fires - but in winter they account for 70% of the (particulate) pollution in the air 1. In Christchurch, New Zealand, 90% of the winter-time air pollution comes from home heating4. Imagine how much cleaner the air in our major cities could be from the simple act of phasing out wood heaters. While I don't have the test figures I would surmise from this that in rural towns where wood heating can be more prevalent than in cities like Sydney and other pollution sources less, smoke from wood heating would account for a much higher percentage of pollution in the air during winter. In fact it is quite possible that the air pollution in some of the rural towns during the heating season can be worse than the suburbs of major cities. This is ironic when it it can be considered that one of the significant benefits of living in a rural town is the (supposed) lack of pollution.

This problem has been recognised in places like Launceston Tasmania where the pollution level from wood smoke is so bad that there are programs in place to subsidise the replacement of the wood heaters 2. The problem has also been recognised in Armidale NSW 3 and Canberra.

Wood smoke is a health hazard in two ways: firstly it contains a cocktail of chemicals many of which are injurious to health; and secondly it contains a large number of ultra fine particles.

Wood smoke contains chemicals that have been proven to adversely affect health. Some of these cause respiratory problems and others are known to cause cancer.4 The chemicals in wood smoke include carbon monoxide (a single wood fire can emit as much as 35 times that of a car!) and many of the oxides of nitrogen1. It can include chemicals such as dioxins and volatile organic compounds, many of which are potentially toxic and have unknown long-term effects. Many of these compounds are in common with those seen in tobacco smoke and car exhausts.4

Wood smoke also contains ultra fine particles. These particles, called PM-10s, (particles less than 10 micron in size,) can be breathed deeply into the lungs, and can exacerbate a whole range of health problems: emphysema, asthma and bronchitis and have even been implicated in heart disease. They’re particularly bad for the very old and the very young4. Wood smoke also contain the smaller particles PM-2.5s1 which can be even more harmful. 

There is double standard between smoke from heaters and car exhaust - if a car was driving around on the roads spewing out of its exhaust even one tenth of the smoke from a poorly maintained and used wood fire heater it would be put off the road very quickly. If the driver continued to use the car fines would have been imposed. However owners of wood heaters can apparently get away with massive pollution on an ongoing basis with little fear of sanction or penalty. This is illogical.

Wood fires have also gained an image of being "environmentally friendly" because the wood that is burnt is seen as a renewable resource. However this depends on the source of the wood - how environmentally friendly is it if the wood is taken from native forests, or worse, old growth forests? (How do you know where the wood is from unless you are in the fortunate position of being able to source wood from your own property - very few people are in this position, especially those in cities and towns.) Even taking fallen wood from the forest floor deprives some forest creatures their required habitat. Most national and state parks usually prohibit the collection of fallen wood for this reason. Wood fires use huge quantities of wood (each using between 1 and 8 kg/h)(5) when you consider the numbers of wood heaters currently in the community (estimated at 1.5 million heaters and 4 million tonnes of fire wood burnt in Australia in 1999)(5). It is environmentally preferable for the wood to be left in the forests or, if harvested, used for high value, long lasting uses, such as high quality furniture and building, rather than the short term release of heat when burnt. Burning of good quality timber is environmentally on a par with wood chipping and pulping. Also, unless you have your own wood lot outside your back door and do all the cutting by hand, using ax and saw, then the collection and cartage of wood for heating purposes requires fossil fuels, for chainsaws and vehicles for distribution. I have even seen fire wood sold in supermarkets wrapped in plastic ($6.99 AUS for 5 kg - $1.40 per kg, $1400 per tonne!). This is both expensive and environmentally damaging.

The other issue with wood heaters is the matter of equity. The users of wood heaters are getting a private benefit, the heat and appearance of the wood fire, however the costs, the degrading of the environmental amenity of the surrounding area and the associated negative health impacts, are borne not just by the user but also by the general community. I have seen arguments that say that wood is the cheapest form of heating (which is in itself debatable - it depends on your wood source) and that to remove wood heating as an option would deprive the less well off of heating. Using this argument you may as well argue that the less well off should therefore be allowed to drive ancient, ill maintained cars that spew out plumes of exhaust gas because that is all they can afford - this is a nonsense. If the cost of heating is an issue for some in the community then this should be addressed by other forms of assistance rather than allowing the lowering of amenity for all (and indeed there are energy subsidies available that recognise this issue).

Another incentive for moving away from wood heaters is simply convenience. With a gas (or other alternative) heater there is no chopping and carting wood, no lighting delays and problems, no requirement to continually feed the fire and no cleaning of the fire box and the associated mess - just turn the knob and nearly instant heat. This by itself is sufficient reason to change by itself, regardless of health and environment benefits.

What Can Be Done

The first step is education. Wood smoke education should be general community education - in the long term it would be hoped that the health risks associated with wood smoke be as well known as cigarette smoke and the smoking chimney as socially unacceptable as cigarette smoking. It would be hoped that some public monies would be provided for this cause (as it is with anti-smoking education). The education can also be targeted at those with wood fires - they are easy to locate - look for the smoking chimney.

Wood smoke education can have two major approaches: health risk and also correct wood heater use.

For many people education on the health risk of wood smoke will be enough incentive to voluntarily change their heating preferences. For example some people who would never dream of smoking a cigarette because of the health risks might not currently associate wood fires with similar health risks. Once they learn of the risks they will change, especially when they realise the highest risk is to themselves and their families - as well as going up the chimney an amount of wood smoke will escape from a wood heater into the house itself, for example when first lighting the fire and at subsequent reloading of wood. There may be some smoke leakage from the firebox seals (although this is not a significant problem with newer well maintained heaters).

There can also be education on the best way to use wood heaters to minimise wood smoke production - for those who after hearing about the risks still opt to continue to use the wood heater, due to limited other heating options or economic reasons. There are massive differences in wood smoke generation between a well used wood heater and a poorly used wood heater. Wood smoke production in a poorly used wood heater can be up to 100 times more than a well used and maintained wood heater. So education in how to properly use a wood heater can have a very significant impact on the amount of wood smoke in the community. If an education program succeeded in decreasing wood smoke in the community by a factor of 10 this would be a significant improvement to community amenity. Continuing wood smoke generated from a heater is also an indication that the wood fire is not being used at its highest efficiency - wood smoke is fuel that hasn't been fully combusted to release all of its energy - it is a waste of money as well as a pollution source. Efficient correct operations of a wood heater includes: the use of correctly stored dry, seasoned hard wood; properly maintaining the heater and chimneys such as cleaning the creosote from the flue yearly; replacing the “Chinaman’s cap” with a parallel rain excluder; applying techniques to minimize smoke such as loading the wood with adequate space around the logs, and putting on a quick burn after lighting or reloading; and the use of wood heaters that meet AS/NZS (Australian/New Zealand Standard) 4013 for particle emissions.4 and generally limiting use of the heater (including not running the heater overnight by chocking the air supply).

The next step would be the regulation of the installation of new wood heaters in urban and semi rural areas, including country townships and other country areas that have a recognised problem. Under this scenario people would be required to apply for a building permit for the installation of new wood heaters. This would allow the provision of educational material on the health risks and on responsible wood heater use and provide a regulatory hurdle. It would also ensure that only the latest technology wood fires were installed.The next step would be banning of all new wood heaters, especially in areas which have reticulated gas. This could be extended to areas without gas.

After this, a program should be put in place to encourage the changeover of existing wood heaters. This would initially target open fires which have appalling efficiency (less than 10% of the energy contained in the wood it transferred as heat to the room5) and worse health risks, especially for the inhabitants of the house - the house can be very easily smoked out internally with an open fire place. Financial incentives, cash grants could be offered for the installation of non wood heater when it replaces a wood heater.

In conjunction with the wood heater replacement program there should be stricter enforcement of emissions standards for those who choose to keep the wood heater and, after a suitable number of warnings, fining of the owners of wood heaters which exceed allowable pollution limits.

While consideration can be given to up-grading existing wood heater to a less polluting model (I understand that wood pellet heaters are quite clean and efficient these days and may be a viable option when gas is not available), if there are alternatives to wood heating these should be given preference - no matter how good a wood heater is it can still be misused or not maintained properly, and wood smoke will occur. No matter how well used, they are always going to put out more pollution into the local community than a gas heater.

Alternatives to Wood Heating

A lot of people already have alternatives to the wood heater installed in their houses. For them it is simply a matter of using the alternative heating when required.

The first alternative for a new heater is reticulated natural gas which is available in most capital cities and a lot of rural cities and towns. It is simply a matter of buying a new heater and connecting up. An efficient natural gas heater has reasonably low green house gas production. (I would prefer a zoned space heating system rather than an unzoned ducted heating system which would heat the whole house, even those rooms not being used, and consequently is environmentally wasteful and expensive to run.) If people like the look of the flame from a wood fire there are gas fired heaters which provide a realistic "fake" wood fire effect (although they are usually a bit more expensive).

The next alternative in areas without reticulated gas is bottled gas, although I understand that this can be expensive.

Reverse cycle air conditioning can also be used. Heating with reverse cycle air conditioning has benefits in that the unit can have a COP of 3 to 4. This means that for every unit of electrical energy used 3 to 4 units of heat is delivered. So when shopping for a reverse cycle air conditioner look for one with a high COP. If the electricity used is from brown coal this means the generation of green house gases (however much less than an electrical resistance heaters). If the electricity used is from a green source then the green house gases generated are minimal.

Use of electrical resistance heaters should be minimised. These are typically the cheap fan forced or radiant heaters, such as bar heaters or portable oil column heaters. (Preferably these should only be used for spot heating or directly heating a person.) Or they can be electrical slab heating - while this may heat the slab with off-peak electricity overnight to minimise the cost of electricity it does not minimise the greenhouse gas production - unless the electricity is "green".

If building a new house (or significant renovation) then the house should be built on energy efficient principles. If built well enough external heating energy (other than the sun) may not be necessary or only required on winter days when there is limited or no sun. For some existing houses it may be straightforward to retrofit additional insulation. This would be very effective in decreasing heating costs for all options.


1. Karl S. Kruszelnicki Pty Ltd 1998 - on the Australian Broadcasting Corporation website - Great Moments in Science (now removed from website)

2.Launceston Air Quality.

3. Armidale Air Quality Group

4. Report from Jackie May broadcast on ABC television on 25 May 2002.

5. Training Handbook for Wood-Smoke Mitigation, John J Todd, National Heritage Trust, 2003

Other References

Launceston Wood heater Replacement Program

Audit finds wood burning heaters failing to meet pollution standards - on 9 June 2004, the 7.30 Report broadcast on the ABC.

Canberra Wood Heater replacement

Department of Environment and Heritage air quality pages.

Department of Environment and Heritage woodsmoke pages.

Clean Air Revival – An American based website.

Clean Air Society of Australia and New Zealand

CABRA – Community Awareness about the health effects of Burning wood in Residential Areas), based in South-East Queensland.

HAPINZ - Health and air pollution in New Zealand 

"Hot Tips" for cleaner and more efficient use of Wood Heaters (pdf).

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