Updated July 2026

Wildfire smoke can affect a workplace or building even when the fire is hundreds or thousands of miles away. Smoke may enter through ventilation systems, open doors, loading areas, windows, and gaps in the building envelope. It can expose outdoor workers, affect indoor air quality, trigger occupant complaints, disrupt operations, and activate regulatory responsibilities.

Employers and building managers can usually determine whether smoke is present outside their facilities. The most important question, though, is what conditions are like at the worksite or inside the building—and what actions are appropriate.

This FAQ explains the health concerns associated with wildfire smoke, the role of fine particulate matter and the Air Quality Index, steps organizations can take before and during a smoke event, workplace requirements, and situations in which professional assessment may be warranted.

What Employers and Building Managers Need to Know

  • Wildfire smoke can travel long distances and affect communities far from the fire.
  • Fine particulate matter known as PM2.5 is the primary pollutant used to evaluate short-term wildfire smoke conditions.
  • Outdoor AQI does not necessarily describe conditions inside a particular building.
  • Indoor conditions depend on filtration, ventilation, building pressure, air leakage, open doors, occupant activity, and building operations.
  • Organizations should decide in advance who will monitor smoke conditions, what information will be used, and what conditions will trigger a response.
  • Several states have wildfire smoke rules or protections for certain workplaces and outdoor workers.
  • Professional evaluation may be appropriate when indoor conditions are uncertain, complaints continue, monitoring results are difficult to interpret, or smoke residue may have affected a property.

What Health Problems Can Wildfire Smoke Cause?

Wildfire smoke can irritate the eyes, nose, throat, and respiratory system. Short-term symptoms may include coughing, wheezing, difficulty breathing, headache, fatigue, chest discomfort, a runny nose, and irritated eyes or throat.

Smoke exposure may also aggravate asthma, chronic obstructive pulmonary disease, heart disease, and other existing health conditions.

People who may face greater risk include:

  • Children
  • Older adults
  • Pregnant women
  • People with asthma or other respiratory conditions
  • People with heart disease
  • People with diabetes or chronic kidney disease
  • Outdoor workers
  • Workers performing strenuous physical activity
  • People exposed to smoke for extended periods

The presence or absence of odor should not be used as the sole measure of exposure. People vary in their ability to detect odors, and an odor may remain even after airborne particle concentrations have fallen. Conversely, fine particles may be present even when the smoke odor is not strong.

Anyone experiencing severe symptoms should seek appropriate medical attention. Employers should also follow applicable procedures for reporting and responding to work-related symptoms. 

EPA wildfire smoke and health resources provide additional information for public-health professionals, employers, and communities preparing for smoke events. 

What Is in Wildfire Smoke?

Wildfire smoke is a complex mixture of particles, gases, and water vapor produced as vegetation, structures, vehicles, furnishings, and other materials burn.

Depending on the source and conditions, smoke may contain:

  • Fine and coarse particulate matter
  • Carbon monoxide
  • Volatile organic compounds (VOCs)
  • Polycyclic aromatic hydrocarbons (PAHs)
  • Ash, char, and soot
  • Other products of combustion 

The composition of the smoke changes according to what is burning, the temperature of the fire, weather conditions, distance from the fire, and how the smoke changes as it travels through the atmosphere.

For most short-term wildfire smoke events, public health agencies focus primarily on fine particulate matter known as PM2.5.

Why PM2.5 Is the Primary Measure of Wildfire Smoke Risk

PM2.5 refers to particles with a diameter of 2.5 micrometers or smaller. These particles are far too small to see individually.

Because of their size, they can travel deeply into the lungs. Some may also pass into the bloodstream. PM2.5 is therefore the principal pollutant used in many wildfire smoke warnings, workplace rules, and public health recommendations.

PM2.5 measurements can be expressed as a concentration in micrograms per cubic meter of air. They may also be converted into an Air Quality Index, or AQI, category intended to help the public understand outdoor air conditions.

AirNow wildfire smoke guidance provides general recommendations for reducing outdoor smoke exposure and adjusting activities as conditions change. The AQI is useful, but it does not answer every question an employer or building manager may have. 

Can Wildfire Smoke Affect a Building Far From the Fire?

Yes. Wildfire smoke may travel hundreds or thousands of miles from the fire perimeter.

Communities far from the flames can experience consequences like these:

  • Hazy conditions
  • Reduced visibility
  • Elevated outdoor PM2.5
  • Unhealthy AQI readings and air-quality alerts
  • Outdoor work disruptions
  • Smoke entering occupied buildings
  • Employee or occupant complaints
  • Increased demand on filtration systems
  • Operational and scheduling concerns

A property does not need to be located in a forested area to face wildfire smoke. Offices, schools, hospitals, apartment communities, hospitality properties, industrial facilities, retail buildings, and public agencies may all be affected when smoke moves into a region.

This makes wildfire smoke a recurring operational and workplace health issue—not only a concern for properties directly threatened by fire.

Can Outdoor AQI Tell Us What Is Happening Inside a Building?

Not necessarily.

The AQI generally describes outdoor air conditions for a geographic area. It does not directly measure the air inside a particular building, room, vehicle, or work area.

Indoor smoke conditions can be affected by:

  • HVAC filtration efficiency
  • The condition and fit of filters
  • Outdoor-air intake
  • HVAC operating schedules
  • Recirculation rates
  • Building pressure
  • Open doors and windows
  • Loading docks and delivery areas
  • Gaps in the building envelope
  • Exhaust systems
  • Occupant movement
  • Indoor particle sources
  • The size, design, and use of the building

Two nearby buildings may experience different indoor PM2.5 levels during the same outdoor smoke event. Conditions may also vary among rooms, floors, entrances, and work areas within one building.

Outdoor AQI is an important starting point. When decisions depend on the actual conditions inside a facility, indoor observations or measurements may also be needed.

Can an Air Sensor Determine Whether Indoor Air Is Safe?

Air sensors can provide useful information, but a number on a display does not explain the entire situation.

Properly selected and deployed instruments may help an organization:

  • Follow changes in particle concentrations
  • Compare indoor and outdoor conditions
  • Identify areas with different conditions
  • Evaluate the apparent effect of filtration or operational changes
  • Determine whether conditions are improving or worsening
  • Document conditions during a smoke event

However, sensor performance varies. Results may be affected by instrument quality, calibration, humidity, particle composition, maintenance, placement, and the way the data are interpreted.

A useful monitoring plan should define:

  • Why measurements are being collected
  • Where instruments will be located
  • What outdoor data will be used for comparison
  • How often readings will be reviewed
  • Who will interpret the results
  • What conditions will trigger action
  • How observations and operational changes will be documented

Air sensor readings should be interpreted in the context of the building, the purpose of the evaluation, outdoor conditions, and the limitations of the instrument. FACS provides guidance on the appropriate use and limitations of air sensors and indoor air quality monitoring in greater detail.

Note: A sensor reading alone cannot determine whether an odor is caused by wildfire smoke or whether ash, soot, or combustion residue remains on building surfaces.

What Should an Organization Do When Wildfire Smoke Arrives?

The appropriate response depends on the severity and duration of the smoke, the work being performed, the building, the people who may be exposed, and applicable workplace requirements.

A practical response may include the following steps:

  1. Check current PM2.5 and AQI information from an authoritative source, such as the AirNow Fire and Smoke Map.
  2. Determine whether state wildfire smoke requirements apply to the workplace or employees.
  3. Identify outdoor workers and others who may experience greater or longer exposure.
  4. Review HVAC operation, filtration, outdoor-air intake, building pressure, doors, loading areas, and other likely smoke entry points.
  5. Reduce avoidable entry of outdoor smoke where doing so is safe and consistent with applicable ventilation requirements.
  6. Consider indoor monitoring when outdoor AQI does not provide enough information for building or operational decisions.
  7. Communicate current conditions and response measures to workers, tenants, students, patients, residents, or other occupants.
  8. Give employees a clear way to report symptoms, smoke entry, or worsening conditions.
  9. Document measurements, observations, complaints, building changes, work modifications, and decisions.
  10. Obtain professional assistance when the organization cannot confidently characterize conditions or determine an appropriate response.

Organizations should avoid relying on a single observation, odor complaint, AQI reading, or low-cost sensor result when significant occupancy, employee exposure, compliance, or operational decisions are involved. Employers operating outside states with specific wildfire-smoke rules should review OSHA wildfire smoke recommendations for employers. 

What Should a Wildfire Smoke Plan Include?

A practical wildfire smoke plan should be developed before smoke arrives.

The plan should identify:

  • Who is responsible for monitoring air quality
  • Which official data sources will be used
  • How frequently conditions will be reviewed
  • What conditions will trigger specific actions
  • How workers and occupants will receive updates
  • How symptoms and concerns will be reported
  • Which work activities can be modified or relocated
  • How outdoor workers will be protected
  • Whether respiratory protection may be offered or required
  • How HVAC systems will be operated
  • What filtration improvements are feasible
  • How smoke entry through doors and loading areas will be reduced
  • Whether cleaner-air rooms or areas will be designated
  • When indoor monitoring will be considered
  • When professional assistance will be requested
  • How actions and decisions will be documented

The plan should be practical enough to use during a changing smoke event. Responsibilities and decision points should be clear before supervisors, facility personnel, or safety professionals are required to act. 

EPA provides a planning framework for schools, commercial buildings, and similar facilities. Organizations should adapt general guidance to the design and operation of their own buildings.

School administrators may also find the FACS guidance on protecting schools from wildfire smoke useful when developing response procedures. 

Can Portable HEPA Air Cleaners Protect a Workplace or Building?

Portable HEPA air cleaners can help reduce airborne particles in individual rooms or defined areas when they are properly selected, sized, operated, and maintained.

They may be useful in:

  • Offices
  • Classrooms
  • Meeting rooms
  • Resident rooms
  • Waiting areas
  • Smaller workspaces
  • Designated cleaner-air rooms

A portable unit should be sized for the room in which it will operate. Ceiling height, air-cleaner capacity, room use, door openings, and the severity of the smoke should all be considered.

The unit should not produce ozone. Filters must also be inspected and replaced as needed, particularly during extended or heavy smoke conditions.

Portable air cleaners are only one possible control. They do not correct:

  • Poor whole-building filtration
  • Uncontrolled outdoor-air entry
  • Building-pressure problems
  • Smoke entering through heavily used doors
  • Poorly sealed filters
  • HVAC systems that are not operating as intended
  • Smoke infiltration through the building envelope

Larger or more complex facilities may require a coordinated strategy involving HVAC filtration, building operations, portable units, space-use changes, monitoring, and occupant communication.

What Wildfire Smoke Requirements Should Employers Know About?

Wildfire smoke requirements vary by state, industry, work setting, employee exposure, and the work being performed.

California, Oregon, and Washington have specific occupational wildfire smoke requirements. Nevada has also enacted protections addressing certain outdoor-worker exposures. Other states may apply general occupational safety requirements even when they do not have a wildfire-specific rule.

Depending on the jurisdiction and exposure conditions, employer responsibilities may include:

  • Monitoring PM2.5 or AQI
  • Training employees
  • Communicating changing conditions
  • Establishing a wildfire smoke response plan
  • Implementing engineering or administrative controls
  • Modifying work
  • Providing respiratory protection
  • Requiring respirator use at higher concentrations
  • Responding to employee symptoms

Because rules and implementation guidance can change, employers should consult current official sources:

Organizations should not rely on a general article as a substitute for reviewing the rule that applies to their operations. Legal or compliance counsel may also be appropriate when regulatory obligations are uncertain.

What Is the Difference Between Regional Smoke and Property Contamination?

Wildfire smoke can create two related but different situations.

Regional Wildfire Smoke Affecting Air Quality

A fire may be located far from the facility while smoke raises outdoor PM2.5 and affects indoor air.

Questions commonly include:

  • Is smoke entering the building?
  • How do indoor conditions compare with outdoor conditions?
  • Is the HVAC system limiting or increasing smoke entry?
  • Are filtration and building operations adequate?
  • How should monitoring results be interpreted?
  • Should work, occupancy, or building operations change?
  • What should be communicated to employees or occupants?
  • How should the response be documented?

This type of situation generally centers on airborne smoke, worker or occupant exposure, indoor environmental quality, and building operations.

Ash, Soot, Odor, or Residue Affecting a Property

A property near a wildfire or structure fire may experience direct deposition of ash, char, soot, or other combustion residue.

Questions may include:

  • Did fire-related residue enter the building?
  • Which rooms, systems, surfaces, or contents may be affected?
  • Is the visible material consistent with wildfire or structure-fire debris?
  • Is cleaning or restoration appropriate?
  • How should the affected area be defined?
  • Was cleaning effective?
  • What documentation is needed for ownership, insurance, legal, or occupancy decisions?

This type of situation may require visual assessment, evaluation of smoke-infiltration pathways, surface sampling, microscopic analysis, and recommendations concerning cleaning or additional investigation. FACS provides structure fire and wildfire smoke assessments to help clients understand and document the effects of smoke and combustion particles on buildings and contents. 

Airborne PM2.5 measurements and surface residue assessments answer different questions. One should not automatically be substituted for the other.

When Is a Professional Wildfire Smoke Assessment Appropriate?

General public-health guidance may be sufficient when smoke is limited, building conditions are well controlled, and the organization already has a clear response plan.

Professional assistance may be warranted when one or more of these conditions are observed:

  • Indoor conditions are uncertain
  • Outdoor smoke appears to be entering the building
  • Employees or occupants report continuing symptoms or concerns
  • Complaints are concentrated in particular areas
  • Monitoring results are inconsistent or difficult to interpret
  • Indoor and outdoor readings need to be compared
  • HVAC operation, filtration, or smoke entry requires evaluation
  • An employer needs exposure-assessment or compliance support
  • Visible ash, soot, char, or combustion residue may have entered the property
  • Smoke odor remains after outdoor conditions improve
  • A building has been exposed to a nearby wildfire or structure fire
  • Cleaning or restoration decisions require technical support
  • Post-cleaning conditions need to be evaluated
  • Occupancy, insurance, legal, or operational decisions require defensible documentation

Indoor conditions may require an indoor environmental quality assessment when smoke entry, occupant complaints, ventilation, or building conditions cannot be adequately characterized through routine observations. 

When the concern involves workers, work activities, or regulatory responsibilities, a workplace exposure assessment may be appropriate.

The scope of an assessment should be based on the question the client needs answered. An investigation intended to evaluate current airborne smoke conditions will differ from one intended to identify deposited combustion residue or evaluate cleaning.

How Can FACS Help?

Forensic Analytical Consulting Services helps employers, property owners, schools, healthcare organizations, public agencies, insurers, facility teams, and other clients understand and manage wildfire smoke concerns.

Depending on the circumstances and the client’s needs, FACS services may include:

  • Indoor environmental quality assessment
  • Exposure assessment
  • Indoor and outdoor particulate evaluation
  • Monitoring strategy and data interpretation
  • Review of building conditions and smoke-infiltration pathways
  • Evaluation of HVAC and filtration factors
  • Visual inspection for ash, char, soot, or combustion residue
  • Surface dust sampling and microscopic analysis
  • Development of practical recommendations
  • Support for cleaning or remediation decisions
  • Post-cleaning evaluation
  • Documentation for operational, insurance, legal, or stakeholder needs
  • Wildfire smoke preparedness and compliance support

FACS uses a practical, data-driven approach to define the problem, collect the right information, and help clients determine what to do next. Additional articles, guidance, and service information are available in the FACS wildfire and smoke resources center.

Concerned About Wildfire Smoke at Your Workplace or Property?

Outdoor AQI can tell you that smoke is affecting a region. It may not tell you what is happening inside your building or whether fire-related residue has affected the property.

Call FACS at (888) 711-9998 to discuss your concerns with an experienced professional. You may also contact FACS online.