Wood heaters provide effective household heating. Wood heaters pollute less than open fireplaces, though can still be a major source of air pollution if you do not operate them properly.
Fine particles cause many of the environmental and health problems associated with woodsmoke. They are a major source of air pollution in winter when people use wood heaters for home heating.
Wood heater emissions and efficiency standards are mandatory in most states and territories. Standards are set by Standards Australia.
States and territories provide best practice guidance for using wood heaters in their jurisdictions. For example, NSW EPA has a range of resources available on how to correctly use wood heaters. For information about wood heaters in your jurisdiction, please visit your local government website.
Impact on human health
The key pollutant from wood fires is particulate matter (PM10 and PM2.5). This is harmful to human health, particularly for high risk groups such as:
- pregnant women
- the elderly
- people with respiratory illness.
The health problems associated with wood heater smoke include:
- chronic lung disease
- heart problems
- premature births and deaths.
Some pollutants from wood heater smoke, such as particles and formaldehyde, are carcinogenic. Chronic exposure can cause heart and lung disease and certain cancers.
Woodsmoke is a problem on very cold, still nights because:
- more people leave their wood heaters burning overnight
- people overload their heater with wood, starving the fire of oxygen and causing it to smoulder and produce a lot of smoke
- smoke hangs in the air at ground level without a breeze to blow it away.
When wood heats to a high enough temperature it breaks down into a complex mixture of gases. These gases burn in the presence of oxygen to give off heat. If there is not enough oxygen or heat, the gases only partially burn. The un-burnt gases will go up the chimney into the air outside. This creates smoke made of chemical components (fine particles and associated gases) such as:
- nitrogen oxides
- carbon monoxide
- volatile organic compounds (VOCs)
- polycyclic aromatic hydrocarbons (PAHs).
The hot embers of a wood fire are the last stage of the burning process before the fire goes out. They are made up of carbon, commonly referred to as 'charcoal'. Almost half the heat from a wood heater comes from these hot embers. The embers burn very cleanly and make hardly any smoke.
If you run your wood heater overnight, there will be much less smoke if you burn the gases off first, before turning the heater down to reduce air supply.
Start your wood heater the right way. This creates a hot, efficient fire with minimal smoke.
To minimise the amount of smoke from a wood heater, you should:
- burn only dry, seasoned, untreated wood
- wait for the fire to establish before adding extra fuel
- open the air controls for a few minutes before adding fuel
- after reloading, wait until the fire is burning before turning the air controls down
- avoid overloading your heater, as this will starve the fire of oxygen and cause it to smoulder
- use small or medium pieces of wood
Many heaters produce fewer emissions than required by the Australian standards. This is due to improvements in design and technology. Purchase a wood heater with the lowest level of emissions possible.
Buying and installing a new wood heater
If you are buying a new heater, make sure it complies with the latest Australian standards.
Check for a compliance plate showing it meets:
- AS/NZS 4012:2014 Domestic solid fuel burning appliances – Method for determination of power output and efficiency
- AS/NZS 4013:2014 Domestic solid fuel burning appliances – Method for determination of flue gas emission.
It must also be installed according to the AS/NZS 2918:2018 Domestic solid fuel burning appliances - Installation.
Local regulations about where and how wood heaters and chimneys can be installed also apply. As these can vary, contact your local council to check before installing a wood heater. Some councils keep a register of licensed installers who will certify that heaters are installed to the standard.
Biomass heating options, including pellet and grain heaters, are more efficient and produce fewer emissions than conventional wood heaters. Pellet fuel heaters burn pellets of compressed sawdust. This is the waste product of sawmilling processes. These heaters use a hopper to feed pellets into the firebox. Pellet heaters have very low emissions and are almost smokeless.
Gas heaters and efficient reverse cycle air conditioners (or heat pumps) are also alternatives in urban areas. They are generally more efficient as they avoid transporting firewood to urban areas, saving energy and emissions.
Improving the thermal efficiency of your house may reduce the need for heating. You can regulate the temperature of a house through:
- wall and ceiling insultation
- thick curtains
- using thermal mass in floors and walls.