Wood Smoke Pollution

The nine counties that surround San Francisco Bay are home to almost seven million residents and an estimated 1.7 million fireplaces and woodstoves. The particulate matter (PM) in wood smoke from these fireplaces and woodstoves has been a health concern in the Bay Area for many years.

Particulate matter is a mixture of solid and liquid particles in the air. The smaller-sized particles - those 10 micrometers or less in diameter (PM10) - are of greatest health concern because they can pass through the nose and throat and lodge deep in the lungs. Included in PM10 is a subset of very tiny particles 2.5 micrometers or smaller (PM 2.5), sometimes called "fine" particles. For comparison, a particle 10 micrometers in diameter is about one-seventh the diameter of a human hair.

Under certain meteorological conditions - cold, stagnant winter evenings - surface based radiation inversions form quickly in the Bay Area and PM levels rise rapidly. By the 1980's, wood smoke became the largest area-wide stationary source of PM in the Bay Area. Studies by the Air District indicated that wood smoke was responsible for an average of one-third of the PM10 in the air basin during the winter months and almost 70 percent of the PM10 in Santa Rosa. In addition, wood burning generates carbon monoxide and toxic air pollutants such as benzene and dioxin.

Since the 1980's, many scientific studies (pdf) have been published that correlate rising PM levels with serious health effects, such as asthma symptoms, decreased lung function, increased hospital admissions and even premature death.

The U.S. Environmental Protection Agency (EPA) has set a national PM emission standard for woodstoves at 7.5 grams per hour. Since July 1, 1990, all woodstoves manufactured in the United States have been required to meet this EPA standard. Previously, unregulated woodstoves averaged 60 grams of PM in an hour.

In 1998 the Air District, with stakeholder input, developed a Model Wood Smoke Ordinance (pdf) for fireplaces and woodstoves as a guidance document for cities and counties that wish to regulate sources of particulate matter in their communities. The ordinance does not ban wood burning in fireplaces but seeks to take advantage of new, cleaner technologies that have been developed to effectively reduce wood smoke pollution. Air District staff work with health agencies and interested residents in the Bay Area to advocate for the adoption of the ordinance, and now 41 cities and eight counties have wood smoke ordinances.

The wood smoke ordinance gives local communities better control over the quality of their lives, contributes to cleaner air, and reduces health costs. It also assists local air districts in attaining and maintaining federal and state PM standards in a reasonable, cost-effective manner.

You CAN Make a Difference! Take These Steps To Reduce Woodsmoke Pollution!

1. Stop Burning Wood!
  - Pollute less by finding a cleaner way to heat your home.
2. Switch to a Gas Fireplace or Insert:
  - Convert your fireplace to gas with a new gas fireplace insert.
3. If You Must Use Wood, Burn Less Wood:
  - Reduce your heating needs by weatherizing your house.
  - Replace your old woodstove or fireplace with a new certified model, and get more heat and less pollution while burning less wood.
4. Change the Way You Operate Your Stove or Fireplace:
  - Burn only clean, seasoned wood and non-glossy white paper.
  - Build small, hot fires instead of large smoldering ones.
  - Burn seasoned cordwood.
  - Watch your chimney for smoke and have it inspected often.
  - Follow your wood heater's operating instructions carefully.
5. Don't Use Your Fireplace on Spare the Air Nights
  - Don't burn wood when the Air District issues a Spare the Air Tonight advisory.
6. Urge Your City or County to Adopt a Wood Burning Ordinance
  - Lobby your local government to adopt the Air District's Model Wood Smoke Ordinance to reduce future air pollution from new homes.


More information about reducing wood smoke pollution is available in our free, colorful Reducing Wood Smoke Handbook (pdf). Community groups can request copies in quantity by calling the Public Information Office at 415-749-4900.