The smoke from any fire (forest, brush, crop, structure, tires, waste or wood burning) releases particles and chemicals when carbon-containing materials burns. All smoke contains carbon monoxide, carbon dioxide, and particulate matter (PM or soot). Smoke can also contain different chemicals, like aldehydes, acid gases, sulfur dioxide, nitrogen oxides, polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, styrene, metals, and dioxins. The particles and chemicals in smoke varies depending on what is burning, how much oxygen is available, and the temperature.

Everyone should avoid smoky areas and limit physical exertion when high levels of smoke can’t be avoided. People with cardiovascular or respiratory conditions like asthma, young children, and older adults may be more at risk of health effects from smoke. If you must be exposed to smokey conditions for long periods of time, proper use of respiratory protection will reduce exposure to the fine particles and gases in smoke.

Inhaling smoke for a short time can cause immediate effects. Smoke irritates the eyes, nose, and throat, and its odor can be nauseating. Studies show that some people exposed to heavy smoke have temporary changes in lung function that makes breathing more difficult. People can also have changes in heart function.  Carbon monoxide and small particles are two common substances in smoke responsible for these health effects.

Inhaling carbon monoxide decreases the body's oxygen supply and causes headaches, reduces alertness, and aggravates a heart condition known as angina. Fine particles from smoke (fine particulate matter, or PM 2.5) can travel deeply into the respiratory tract, reaching the lungs. Inhaling fine particles can cause a variety of health effects, like respiratory irritation and shortness of breath. It can also worsen medical conditions such as asthma and heart disease. Physical exertion can make these health effects worse. Once exposure stops, symptoms may last for a couple of days, but will likely improve.

Anyone with symptoms from smoke or bad air quality should contact their health care provider. You may also want to talk with a health care provider about your health risk when smokey air or poor air quality cannot be avoided.

Exposure to smoke can also increase your risk for long-term (chronic) health effects. People who live in areas with higher fine particulate air pollution and those who breathe air containing fine particles over long periods have a higher risk of cardiovascular disease and mortality. Frequent exposure to smoke even for brief periods can also increase your risk for long-term health effects. Scientists have studied the risk of long-term health effects in firefighters who frequently breathe smoke. Some of these show a higher rate of cancer, lung disease, and cardiovascular disease, while others do not.