Wood smoke from wood-fired home heaters

Last updated: 01 August 2003

What is wood smoke?

Wood smoke is a complex mixture of gases and particles. The gases and particles are air pollutants. The main air pollutants in wood smoke include carbon monoxide, nitrogen oxides, air toxics and particulate matter. The amount, or concentration, of air pollutants in wood smoke emitted from a home heater will actually vary depending on:

• the way the wood burns
• the heating appliance used
• the quality of the wood fuel.

Higher levels of air pollutants are typically generated during fire start-up and where a fire is poorly managed, ie. reducing airflow to the heater allowing wood to smoulder. In some cases, higher levels of air pollutant emissions can occur for the duration of heater use, especially where a heating appliance is performing poorly or where wood with high moisture content is used.

In areas where numerous wood-fired home heaters may be in use, wood smoke produced by each heater can combine, causing high levels of pollution in a local area, particularly on cold still nights.

Wood smoke exposure and health effects

Exposure pathways
Exposure to wood smoke from home heaters can occur in a number of ways including:

• inside a home where a wood heater is used (ie self-contamination)
• outside the home where a wood heater is used (ie effect on neighbouring homes)
• wood smoke contamination of the air inside homes that do not use a wood heater (ie outdoor air penetration)
• air pollution from wood heaters within local area persisting in the outdoor air, especially during times when weather conditions are cold and still.

Key wood smoke air pollutants and health effects
Carbon monoxide (CO) is an invisible and odourless gas that can cause toxic effects in humans by depriving the body of oxygen, impairing thinking and reflexes. CO levels will rise in a home where a wood-fired heater is in use. A poorly installed, improperly vented or leaking wood heater can cause excessive levels of CO in the home, and can lead to CO poisoning, which may result in death at very high concentrations. Many people can experience flu-like symptoms from moderate CO exposure, while at lower levels of exposure people can experience headaches, fatigue or chest pain. Permanent health effects to the heart and brain can
result from extended exposure to high levels of CO.

Particulate matter (PM) or fine particle pollution can affect the human respiratory and cardiovascular systems. Fine particles can cause a variety of temporary or short-term health problems, including itchy or burning eyes, throat irritation, runny nose and illnesses like bronchitis. Particles can aggravate existing heart and lung conditions such as angina, chronic bronchitis, emphysema and asthma. People with vascular complications from diabetes are also particularly susceptible to the effects of fine particles. Decreased lung function in children is also associated with high particle levels.

Australian studies have demonstrated that PM levels in homes with wood heating are much higher than in homes without wood heating, and that the use of wood-fired home heaters in many regional towns is associated with elevated indoor levels of PM, even in homes that do not use wood heaters.

Symptoms from exposure to high levels of fine particle pollution can occur for many days after wood smoke is inhaled, so people with a related medical condition such as asthma need to remain vigilant with their treatment programs.

Air toxics are airborne pollutants that are associated with a wide range of health effects. These effects range from eye irritation and headaches to more serious effects such as damage to the respiratory, nervous, reproductive, developmental and immune systems. Some air toxics are known to, or suspected of, causing cancer.

Polycyclic aromatic hydrocarbons (PAHs) are a mixture of organic compounds that form some of the air toxics generated during wood burning, especially if a woodheater is poorly operated. Some of these compounds are suspected of causing cancer.A recently completed study in NSW has shown that PAH levels are highest in winter in regional towns where wood burning is a popular form of home heating.

Health precautions - what can I do?

People that can be most affected by wood smoke include:

• those suffering from existing cardiac or respiratory conditions, such as asthma
• those with vascular complications from diabetes
• infants and very young children
• frail older people.

If you have a wood heater:

• make sure you operate it properly to minimise smoke generation
• ensure adequate fresh air enters the room to prevent CO build-up
• be alert to symptoms such as drowsiness, as this can indicate high CO levels
• consider installing a less polluting form of heating, such as flued gas or electric.

To protect your health during times when wood smoke around your home or local area is a problem, the following precautions can help to minimise possible health effects:

• avoid outdoor physical activities when wood smoke is present
• staying indoors with windows and doors sealed provides some protection
• if you suffer from heart or lung disease and you notice symptoms.

Ensure you take your regular medications, rest, and seek medical advice if symptoms do not settle.

Related links

• More on indoor air pollution  http://www.health.nsw.gov.au/publichealth/environment/air/indoor.asp
• Unflued gas heaters  http://www.health.nsw.gov.au/factsheets/environmental/gas_heaters_fs.html