Wood smoke produces particles and a variety of gases, all of which may impact allergic conditions and asthma. These substances include:

• Particle pollution. Occurs when tiny particles enter the air from power plant emissions, wood burning and other sources. People can easily inhale these microscopic particles, which then penetrate the body’s defense system. These particles are particularly harmful because they are small enough to settle inside lung tissue, and may pass through the lungs into the bloodstream. Particle pollution has been linked to increased rates of asthma, heart attacks, strokes and lung cancer, as well as reduced life expectancy.
  
  
• Carbon dioxide. A colorless, odorless gas that can deprive the body’s tissues of oxygen. It is commonly generated by wood stoves, cooking and heating systems.
  
  
• Carbon monoxide. An odorless gas that reduces the oxygen–carrying capability of blood. It is the byproduct of indoor fuel–burning appliances such as gas stoves, fireplaces, wood stoves and unvented kerosene or gas space heaters. In high doses, carbon monoxide is lethal. Children are more susceptible to the effects of carbon monoxide exposure.
  
  
• Nitrogen dioxide. An odorless gas that causes bronchial hyperresponsiveness (an exaggerated airway response). It is the byproduct of many of the same products that create carbon monoxide, including indoor fuel–burning appliances such as gas stoves, fireplaces, wood stoves and unvented kerosene or gas space heaters. Children and people with asthma may be more susceptible to the effects of nitrogen dioxide.
  
  
• Formaldehyde. Substance capable of acting as a respiratory irritant.
  
  
• Benzopyrene. Substance capable of causing cancer when inhaled in large amounts.