Stage 1 fire restrictions, enacted for unincorporated areas of western Boulder County.

Wood Smoke Impacts
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Wood Smoke Impacts

Health Impacts of Wood Smoke

Fireplaces and wood stoves produce smoke when wood doesn’t burn completely and, if operated incorrectly, even the most modern wood-burning devices can produce smoke. Smoke is made up of a complex mixture of gases and fine particles produced when wood and other organic matter burn, including over 100 hazardous chemicals that are toxic and carcinogenic (cancer-causing). When breathed in, these fine particles can lodge in our lungs.


Even occasional exposure to wood smoke can cause watery eyes, stuffy noses, and chest tightness. Smoke particles can also cause:

  • Headaches
  • Lung and eye irritation
  • Decreased alertness
  • Nausea
  • Fatigue
  • Rapid breathing
  • Chest pain
  • Confusion
  • Impaired judgment

For some, smoke can also aggravate cardiovascular problems such as angina and respiratory issues such as asthma, emphysema, and bronchitis.

Environmental Impacts

Wood smoke is a significant contributor to the air pollution problem in the Denver Metro Area. Using a non-certified wood stove for four hours emits as much carbon monoxide as driving a car 20 miles.

Wood burning:

  • Can contribute up to 20% of the Particulate Matter (PM-10) in the air. Other sources of particulates include street sanding and vehicle emissions.
  • Contributes 15% of the carbon monoxide in the air. Other sources are vehicle emissions and fossil fuel combustion. Carbon monoxide can bind with blood hemoglobin and prevent oxygen from reaching the body.

To protect the health of those in the home, and the homes nearby, the best option is to avoid using wood-burning stoves entirely, replace them with a non-burning option, or use a certified wood stove. Cleaner burning natural gas, wood, or pellet appliances minimize air pollution; are more energy efficient; provide better temperature control; and can be used on mandatory no-burn Air Quality Action Days.

Woodburning Pollutants

Burning wood produces many harmful chemicals that damage indoor and outdoor air and can cause health problems.

Fine Particulate Matter (PM-10)

Fine Particulate Matter are tiny dust and soot particles, smaller than 10 microns in diameter, that are small enough to be inhaled and trapped in the lungs. Inhaled particles are a concern because of their potential to cause cancer and other respiratory conditions.

Carbon Monoxide (CO)

Carbon Monoxide is a colorless, odorless gas and a chemical asphyxiant: it binds to hemoglobin in the blood and prevents hemoglobin from transporting needed oxygen throughout the body.

Carbon Dioxide (CO2)

Carbon Dioxide is primarily an indoor air contaminant and is a greenhouse gas which (may) contribute to climate change. Carbon Dioxide is a simple asphyxiant that displaces the available oxygen in a room. Health effects include increases in respiration, changes in blood chemistry and decreases in the ability to perform strenuous exercise.

Nitrogen Oxides (NO & NO2)

Nitric Oxide (NO) is a precursor to NO2. Both gases are formed by incomplete combustion of fuels and contribute to “acid rain”. Nitrogen Dioxide (NO) is a reddish-brown gas that gives smog its characteristic color. NO and NO2 can interfere with the body’s ability to transport oxygen.

Sulfur Dioxide (SO2)

Sulfur Dioxide is a colorless, gas with a characteristic “rotten egg” odor detectable at certain concentrations. Sulfur Dioxide can easily react with water in the atmosphere to form Sulfuric Acid, a major component of acid rain. When SO2 combines with particulates, it can be corrosive and potentially carcinogenic. Sulfur Dioxide adversely affects the upper respiratory track.

Other Hazardous Chemicals

There are over 100 hazardous chemicals released from wood burning that can be toxic and carcinogenic (cancer-causing). For example, Benzene and Formaldehyde are two carcinogens released from burning wood.

Indoor Air Pollutants of Concern

Wood smoke pollutants can also be released into the home when stoves or fireplaces are improperly installed or vented, when stove doors are opened during burning, or when the stoves are poorly maintained and operated. These pollutants are similar to the outdoor air pollutants mentioned above and can pose the same health risks.

Carbon monoxide and nitrogen oxides are the indoor air contaminants of primary concern. In addition, improperly vented stoves can release water vapor that can condense inside the house and provide and excellent environment for microbial (fungal or bacterial) growth.

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