Wildfires

Wildfire Smoke Exposure

Last Updated: June 03, 2025
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The following information replaces Fact Sheet No. 018-0623 and is provided for use by technical and medical personnel for assessing and managing the risks associated with wildfire smoke.
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​Wildfires across the United States present a significant risk to both life and property. Military personnel are often involved in fire response efforts. Smoke inhalation risks vary with fire intensity, proximity, work activity, weather, and terrain. Smoke levels are highly dynamic and difficult to predict accurately for more than a few hours. ​


​S​​moke Composition

Wildfire smoke from wood and natural debris is usually a mixture of:

  • Particulate matter
  • Gases: carbon dioxide, carbon monoxide (CO), water vapor, nitrogen oxides, sulfur dioxide
  • Trace minerals
  • Thousands of organic compounds (e.g., acrolein, benzene, formaldehyde, polynuclear aromatic hydrocarbons)  

Composition varies with fuel type, fire temperature, and wind speed.  

Potentia​​​​l ​Smoke Health Effects

  • Inhalation Hazard: ​Primarily from airborne particulates, causing respiratory tract irritation, coughing, and breathing difficulties.
  • Eye Irritation: Particulates can also cause temporary eye irritation.
  • Carbon Monoxide (CO): This chemical asphyxiant is a colorless, odorless gas that can lead to headaches, dizziness, visual impairment, and death. 
  • Irritants: Formaldehyde and acrolein contribute to irritation.  

Individual risk depends on exposure level/duration, age, health status, and other factors. Short-term wildfire smoke exposure has a low cancer risk.  

Additional H​​e​​​alth and Safety Concerns

  • Thermal Burns: Hot smoke and gases can burn the respiratory tract.  
  • Physical Burns: Direct burns from fire exposure.
  • Heat/Cold Stress: Fluctuations in temperature can be a major concern. 
  • Electrical Hazards: Damaged power lines pose a risk. 
  • Hazardous Materials: Damaged tanks, drums, and pipes can contain hazardous materials.
  • Fall Injuries: Slips, trips, and falls are common. Terrain may be uneven. Smoke can obscure vision.
  • Unstable Structures: Damaged walkways, parking lots, roads, and buildings can be dangerous.
  • Displaced Animals: Wild and domesticated animals may seek shelter in unusually places. Stress can change their temperament.
  • Vehicle Accidents: Firefighters may be at risk for injuries related to crashes while operating modified vehicles. Smoke can obscure vision.

For more information on the threats to wildland firefighters please visit the CDC's National Institute for Occupational Safety and Health (NIOSH) Firefighting Wildland FiresExternal Link​ webpage.  

Ind​​​oor Air Quality

Wildfire smoke can enter buildings through:

  • Open windows and doors
  • Cracks in structures
  • Ventilation systems (e.g., fans, HVAC intakes)  

Reducing smoke exposure is crucial, especially for vulnerable populations (children, older adults, those with heart/lung disease). Evacuation orders from local officials must be followed. In situations where wildfires do not threaten homes and buildings, local officials may advise you to stay indoors because of higher smoke levels.  

Smoke Exposure Reduction

  • Keep windows and doors closed; use fans/AC to stay cool.  
  • Consider high-efficiency filters for HVAC systems.  
  • Close outdoor dampers and set HVAC to recirculate.  
  • Ensure a tight seal for window AC units; avoid use if the outdoor damper can't be closed.  
  • Avoid indoor sources of particulates and by products: smoking, gas/propane/wood stoves, aerosols, frying/broiling, candles/incense, and vacuuming (unless using a high-efficiency filter).  
  • If using a generator, follow manufactures recommendations.
  • Limit strenuous activity​, which increases respiration.  
  • Use an N95 or P100 respirator if going outdoors.  
  • Ventilate the building when air quality improves.  

Learn ​​more about wildfires and indoor air qualityExternal Link. 

Worke​​r Safety

Title 29 Code of Federal Regulations, Part 1910, Subpart LExternal Link, Occupational Safety and Health Administration covers fire protection standards.

Outdoor work during wildfires necessitates safety measures.  

  • AirNOWExternal Link​ PM2.5 Air Quality Index (AQI) can inform decision-making.  
  • California Occupational Safety and Health AdministrationExternal Link designates AQI for PM 2.5 above 151 as unhealthy and recommends worker protections.  
  • Implement a system for workers to report smoke hazards.  
  • Train employees on health effects.  
  • Encourage prompt medical attention for affected workers.  

Exposure reduction strategies:

  • Relocate work, reschedule, or modify schedules.  
  • Provide filtered-air structures/vehicles.  
  • Implement work-rest cycles and ensure water intake (TB MED 507External Link). ​


Easy Work = weapons maintenance, marksmanship training, drill and ceremony
Moderate Work = patrolling with a 30-pound load, low and high crawl, digging a defensive position
Heavy Work = patrolling with a 45-pound load, 4-person litter carry (180 pounds), jogging 4 mph
​Very Heavy Work = 2-person litter carry (150 pounds), move under direct fire, obstacle course

Firefighter Considerations

  • Refer to Personal Protective Equipment for Wildfire Firefighters for respirator/PPE guidance.  
  • Air-purifying respirators do not remove CO; use a CO monitor (alarm at 25 ppm) in areas with potential CO exposure.  
  • Retreat if CO levels exceed 25 ppm.  
  • Establish heat/cold stress programs and ensure worker training.  
  • Evaluate tasks for hazards and provide appropriate training/PPE.  
  • Military team leaders should coordinate with on-scene commanders and safety managers and adhere to site safety requirements.
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