Woodheaters and open fireplaces are often the major contributors to outdoor air pollution levels in cities and towns during winter. The health effects of wood smoke exposure include increased respiratory symptoms, increased hospital admissions for lower respiratory infections, exacerbation of asthma, and decreased breathing ability.

In residential areas, wood stoves and fireplaces contribute the largest portion of particulate matter air pollution. In addition to the particulate matter in wood smoke, emissions also contain carbon monoxide, nitrogen dioxide, sulfur dioxide, hydrochloric acid, formaldehyde and known carcinogens such as polycyclic aromatic hydrocarbons and dioxin.

The American Lung Association recommends that individuals avoid burning wood in homes where less polluting heating alternatives are available. If you heat your home with wood, the following steps can be taken to minimize the expense, health and environmental effects of indoor wood burning:

1. Never burn:

  • Plastics
  • Glossy magazines or newsprint
  • Painted or treated wood
  • Foil or metallic-coated gift wrap
  • Particle board
  • Household garbage (diapers, plastic bags, etc.)
  • Plywood
  • Rags or fabrics made of synthetic materials

These items release toxic chemicals into the air that can be harmful to your health and damage your stove or fireplace.

2. Split your firewood

Wood dries from the surface inward, so un-split wood dries very slowly. The more surface wood is exposed by splitting, the faster the wood will dry. Stack the wood loosely to promote air circulation.

3. Burn seasoned firewood only

The time it takes freshly split wood to become fully seasoned will vary with the type of wood, its thickness, and the weather. As a general rule, however, one should allow a year for wood to dry for efficient, clean indoor burning. Cracks in the ends of the wood are an indication that it is fully seasoned and ready for burning. You can also test whether the wood is fully seasoned by striking two pieces together. Dry wood gives a sharp ‘crack’ while unseasoned wood sounds more like a dull ‘thud’.

Unseasoned firewood provides less heat energy when burned, yet releases more smoke and contributes to hazardous creosote buildup in chimneys.

4. Store wood outside, covered on top with sides open to air

Cut, split and stack firewood in a place sheltered from the weather, but not covered on the sides, so as to optimize air circulation. Block up the bottom row of wood several inches off the ground. During snowfalls, throw a tarp over the woodpile to keep blowing snow out of the stacked wood.

5. Store only a small amount of wood inside your home.

Bringing large amounts of firewood into the home to ‘pre-dry’ is counter-productive, and may release excess humidity into the room. When lifting from the woodshed into the carrying box, or wood sling, a quick tap against a hard surface will release any spiders that otherwise will be brought into your home.

6. Split wood into pieces 4-6 inches in diameter.

Firewood will burn cleaner when more surface area is exposed to the flame. Use the smaller split pieces to get the fire started, and only use larger pieces of wood once the fire is well established.

7. Make sure your fire is getting enough air.

This will ensure it burns hot and clean. Check the air intake of your heater to ensure there are no blockages from dust balls and spider webs. If you have a through-floor intake, check to see that the screen is brushed clean and not obstructed by insect debris or spider webs.

A properly burning fireplace is hotter, produces less smoke and is more efficient. This means more warmth for less money and less impact to your health.

8. Don’t stuff too much wood inside the firebox.

Overloading the firebox can reduce the amount of air needed for ideal combustion. Refuel more often with smaller loads with the air inlet open wide to keep the fire burning briskly. If you need to shut the fire down, wait until it is well-established before turning down the damper. If you throw a fresh log in just before closing the damper, it may smolder for some time before reaching a cleaner combustion stage.

9. Let your fire go out at night.

To reduce the level of wood smoke pollution in towns and cities it is recommended that you do not burn your wood heater overnight on reduced air flow. This will save you some wood and help your stove and chimney remain cleaner for a longer period of time. It will cost less to let your wood heater go out over night and run an electric heater in the morning for 2 hours, than to keep your wood heater burning through the night.

Common Wood Burning Questions:

How does wood smoke rank in comparison to other air pollutants?
There are many types of air pollutants, and wood smoke is ranked in comparison with the other types of air pollutants. In the northern US and Canada, residential wood smoke is said to account for 25 percent of all fine particulates, 15 percent of the volatile organic carbons (VOCs) and 10 percent of the carbon monoxide.

In certain communities, there have been cases where wood smoke has been the source of most of the particulate matter found in the air. This has occurred in densely populated urban areas and in valleys that are pinned in by mountains so that the wood smoke doesn’t dissipate; instead, it settles back on the town.

Is there much difference in the efficiency of different woodstoves?
In response to the public concern over pollutants caused by wood burning, the Environmental Protection Agency issued rules in 1988 that forced manufacturers of wood stoves to improve their products. The older stoves, pre-EPA-certification, would typically emit 40 to 60 grams of fine particulates into the air every hour. After manufacturers were required to meet EPA standards, the allowable limit was set first at 8.5 grams per hour; in 1990, that limit was cut to 7.5 grams per hour (4.1 grams for catalytic stoves). These newer models are also safer to use because cleaner burning fires produce less creosote buildup in chimneys, which is a leading cause of chimney fires.

Is it OK to burn designer logs?
Designer logs have low amounts of energy output. If you are burning logs simply for ambiance, then designer logs will work adequately. However, they are not recommended for meeting your heating needs.
Unlike pellets that are made of sawdust bound together by the natural cellulose within the wood, designer logs are often bound by spent bitumen oil. If you do not know the ingredients in your fake log, it is recommended that you do not burn it. There are no statistics on how the deposits may damage your stove or fireplace, or about the toxins released from the binding agents.


Burning wood for home heating is still the most practical choice for many people in North America. To minimize the pollution from wood smoke, and to maximize the heat energy potential of the wood, homeowners can benefit by understanding the basics of efficient wood burning and woodheater maintenance.

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