Wood heating is the largest source of smoke (fine particle) pollution during winter. Making matters worse are the stable weather patterns during winter that trap smoke near the ground.
Wood smoke is a complex mixture of fine particles, many of which are toxic and known to cause cancer. Breathing wood smoke can harm everyone, but children are most vulnerable because their lungs are still developing. Also at higher risk from wood smoke are infants, the elderly, and those with existing heart and lung ailments. Health-related studies are linked at the bottom of this page.
Today's new wood stoves burn much cleaner and efficiently, but how the stove is operated is the biggest factor in how much it smokes. The goal is to see only heat waves or just a wisp of smoke from the chimney.
Review this brochure and watch this 5-min video on operating your wood burning device efficiently.
State law prohibits excessive chimney smoke. Smoke is measured as opacity. Smoke so thick you can't see an object through it is considered 100% opacity. Smoke is in violation when it obscures an object by more than 20%.
Pictured on the right are smoke densities of 20%, 40% and 80%.
After start-up, check the chimney. If you see more than heat waves, provide more air (open your damper) to the fire.
Smokey chimneys may also be caused by burning firewood that has not adequately dried. Wood should be split, stacked and loosely covered to dry at least 9-12 months.
Manufactured logs and pellets may be burned in your wood burning device. Burning anything other than natural firewood or manufactured logs/pellets is prohibited under state law.
Devices Sold, Installed
Any woodburning device offered for sale, sold, given away, or installed in Washington must meet the state’s emissions standards of 4.5 grams/hour for non-catalytic and 2.5 grams/hour for catalytic devices. Before selling, purchasing or installing a wood burning device, check with Spokane Clean Air. A permit and inspection is required for installation. Call your city or county building department for details.
Lists of stoves, fireplaces and inserts that meet Washington Emissions Standards are linked from Ecology’s webpage.
Type of Device
|Catalytic wood burning devices||2.5 grams per hour|
|Non-catalytic wood burning devices||4.5 grams per hour|
|Factory-built fireplaces and masonry heaters||7.3 grams/kilogram|
- A Quick Guide on How to Select a New Stove for Home Heat (5 mins) - Different fuel choices come with an array of environmental, economical and health considerations. If you are considering a wood stove or fireplace insert for your home, or upgrading your old wood stove to something that heats cleaner and more efficiently, take a few minutes to determine which device and fuel choice best fits your needs.
Temporary Burn Bans and Exemptions
Temporary burn bans are issued when fine smoke particles become concentrated and are not readily dispersing due to weather conditions. The type of ban depends on the level of pollution and weather forecast. Burn ban details and exemptions to burn bans.
Health Impacts from Wood Smoke
Several studies have been conducted over the years linking fine wood smoke particle exposure to adverse health effects. A leading researcher on the topic is Dr. C Arden Pope III, of BYU. Below are materials from a webinar Dr. Pope presented on July, 28, 2011.
- PM Health Effects from Wood Smoke (PDF) (73pp, 5.5mb)
- PM Health Effects from Wood Smoke (Powerpoint) (73pp, 20mb)
- Webinar audio recording with slides (MP4) (56mb)