When considering the dangers of wildfires, thoughts of fleeing your home while a raging wildfire rapidly approaches can easily consume your imagination. However, the number one cause of death from fires is smoke inhalation.

Inhaling smoke damages your body in one or both of the following ways:

• by robbing it of oxygen
• through particulate matter irritation

Smoke inhalation is particularly dangerous because you may not show symptoms until 24 to 48 hours after exposure. 50–80 percent of fire deaths are from smoke inhalation.¹

Read on to learn how to help protect the health of yourself and your loved ones, and learn some wildfire smoke safety tips to rest assured that you’ve taken the necessary wildfire safety precautions to reduce the consequences of toxic wildfire smoke.

What’s in wildfire smoke?

Wildfire smoke is a mixture of thousands of individual compounds, including harmful particles and gases that pose a severe health risk to anyone (including pets) nearby and downwind from a fire.

Wildfire smoke often contains:

• water vapor

• particulate matter

• trace minerals

• carbon dioxide

• carbon monoxide

• nitrogen oxides

• hydrocarbons and nitrogen oxide compounds that contribute to elevated ozone (O₃) levels

• volatile organic compounds (VOCs), including acrolein and formaldehyde (potent respiratory irritants)

Wildfire smoke often contains fine (PM2.5) and ultrafine particles that can be absorbed directly into your blood stream and reach any organ or area of your body.

Pictured: The typical contents of wildfire smoke, including ultrafine particles (≤ 0.3 microns), PM2.5 (2.5-10 microns), acrolein, PM10 (> 10 microns), formaldehyde, carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxides, and hydrocarbons. Source: IQAir

Wildfire smoke composition depends upon multiple factors, including:

• the types of wood and vegetation burning

• the moisture content

• the fire temperature

• wind conditions

• other weather-related influences

The primary pollutant threatening the health of those nearby and downwind of a wildfire is particulate matter. Wildfire smoke often contains fine (or PM2.5) and ultrafine particles. These tiny airborne particles are the most dangerous to your health.

Fine particles (smaller than 2.5 microns) penetrate deeply into your lungs.

The most dangerous are ultrafine particles (smaller than 0.1 microns), which represent 90% of all airborne particles. These particles are tiny and can be absorbed directly into your bloodstream. Once in your blood, they can reach any organ or area of your body.

Wildfire smoke and at-risk populations

Most healthy adults will recover from smoke exposure. However, certain individuals are more at risk for severe health consequences, including:²

• Young children. Children whose lungs are still developing are considered more vulnerable, regardless of whether they have a pre-existing condition.

• Pregnant women. Wildfire smoke inhalation puts pregnant women and their unborn children at a higher risk than the general population.

• Older adults. This population is at-risk due to an increased rate of pre-existing heart and lung disease.

• Anyone with a respiratory disease. Individuals with emphysema, chronic bronchitis, COPD, asthma, or another respiratory disease are at-risk.

• Individuals with heart disease. Circulatory diseases include high blood pressure, vascular diseases, heart failure, and cerebrovascular conditions. These conditions make sufferers susceptible to heart attacks, transient chest pain, heart failure, stroke, and sudden death from cardiac arrhythmia.

Young children, pregnant women, older adults, and people with respiratory and cardiovascular pre-existing conditions may find that they experience more severe symptoms and find it harder to breathe.³

The full impact of wildfire smoke is not yet fully understood. A 2017 review in Environmental Toxicology and Pharmacology found that there are still important study opportunities for exploring the long-term health implications of smoke exposure, smoke exposure recovery, and additional smoke inhalation health impacts for children.⁴

Exposure to smoke can be dangerous simply due to the microorganisms within the smoke. A 2020 study in Science magazine noted that microorganisms, such as bacteria and fungal spores, comprise some of the particulate matter found in smoke.⁵ The study theorizes that infectious disease may be spread as bacteria and fungi become part of smoke’s particulate composition.

How wildfire smoke behaves

Many factors affect wildfire smoke behavior, such as:

• weather

• geographical terrain

• the stage of the fire

• wind

Use the live, interactive air quality map below to see how weather, wind, and location can impact the behavior of wildfire smoke near you.

Windy conditions generally cause smoke to mix with larger volumes of air to lower smoke concentrations. However, strong winds also can spread fires more quickly, causing larger fires with greater impact.

Regional weather can be the dominant determinant in how a fire behaves as well as how smoke affects surrounding areas. However, regional weather systems can spread fires quickly and result in larger fires with more smoke generated, creating the potential for even greater impacts.

Strong regional weather systems can also dominate a fire’s behavior for days and be the determining factor of where and how smoke will affect an area.

Smoke can travel for miles beyond its source. In 2020, smoke from wildfires in the western United States drifted for nearly 5,000 miles, eventually being detected in Europe.⁶

Wildfire safety tips

Wildfire smoke events can occur seemingly without warning. But there are steps you can take to prepare yourself using appropriate safety precautions for wildfires.

• Keep the air clean in your home. Keep windows and doors closed closed and seal off any openings to the outside, including vents, to help prevent outdoor smoke from getting in. When using an air conditioner, be sure to set it to re-circulate and close the fresh-air intake. Filter the air when ventilating the space. An air purifier for wildfire smoke, will help remove smoke particles of all sizes down to 0.003 microns from the indoor air and help control ozone levels. This is critical if you live in an urban area downwind (even remotely) from wildfires.

• Stay indoors as much as possible. This tactic is most useful in buildings that effectively stop outdoor air from getting inside. If you need to travel by car to leave or evacuate an area affected by wildfire smoke, use a car air purifier to help keep your vehicle interior air clean as you pass through smoky or polluted areas. You can also use a portable, personal air purifier to access clean air where other air filtration systems are not available.

• Wear a mask outdoors. Only use an air pollution mask with an N95, KN95, N100, or FFP2 rating to help.

• Avoid activities that further pollute the indoor air. Avoid burning candles, using the fireplace, or even vacuuming unless you own a high-performance HEPA vacuum cleaner. All of these activities can otherwise become additional sources of indoor air pollutants.

• Monitor your indoor air quality. Use an air quality monitor to track levels of indoor pollutants like PM2.5 and CO₂ from smoke and other indoor pollution sources. Take action if indoor air pollutants rise to dangerous levels by running an air purifier, circulating fresh air through your HVAC system, or leaving your home temporarily if indoor air becomes unsafe to breathe or your home is threatened by wildfire.

• Use an air quality monitoring app to keep track of pollutants in your environment. The AirVisual app displays real-time hyperlocal data from over 80,000 sensors around the world. The app also tracks up to six key wildfire pollutants, such as PM2.5, CO₂, and NO₂, so that you have the best picture of your local air quality during a wildfire and can take action to help protect your health.

Wildfires are increasing in frequency and intensity. Wildfire smoke can negatively affect your health, even if you’re far away from the actual fire. Learn to protect the health of yourself and your family, and rest assured that you’ve taken the necessary precautions.

During a wildfire, it’s also important to monitor your local air quality to see how wildfire smoke will affect your outdoor air.

The takeaway

Wildfires are increasing in frequency and intensity. Wildfire smoke can negatively affect your health, even if you’re far away from the actual fire. And while wildfire smoke may be a warning sign of imminent fires, smoke also delivers its own set of risks for people living miles beyond the source.

Though smoke pollutants carried on the wind may be invisible, their impacts are felt by those most at risk. Smoke pollutants pose health threats that range from irritation and cough to more serious respiratory and cardiac risks.

By helping control smoke pollutants that threaten our indoor air quality through monitoring and air purification, it's possible to help manage wildfire smoke health risks.